Hyperglycemia-induced mitochondrial superoxide overproduction activates the hexosamine pathway and induces plasminogen activator inhibitor-1 expression by increasing Sp1 glycosylation

Anacardium occidentale leaves extract and riboceine mitigate hyperglycemia through anti-oxidative effects and modulation of some selected genes associated with diabetes

Background

Diabetes mellitus (DM) is one of the leading causes of death globally and complications of DM have become a major health concern. Anacardium occidentale is a plant widely recognized for its hypoglycemic properties and traditionally used in developing nations as remedy for DM treatment. Riboceine is a supplement that enhances production of glutathione and known for its vital role in supporting cellular function. This study was designed to evaluate the antidiabetic and antioxidant potential of riboceine and ethanolic extract of A. occidentale leaves in streptozotocin (STZ)-induced diabetic rats.

Method

Twenty-nine adult male Wistar rats were induced with DM intraperitoneally using a single dose of STZ (70 mg/kg). The STZ-induced rats were divided into groups and administered the same dose (100 mg/kg) of A. occidentale leaves extract and riboceine via gastric gavage at the dose (100 mg/kg) for seventeen days while metformin (40 mg/kg) was used as positive control. Fasting blood glucose and weight of the model rats were examined periodically. Activities of total protein, creatinine, urea, antioxidants (SOD, GSH and GPX), and level of serum insulin were determined. Expression of diabetes related genes including pancreas (Insulin, pdx-1, P16NK4A, and Mki-67), Liver (FAS, ACC, and GFAT) and KIM-1 genes were also determined.

Results

Data showed that treatment of STZ-induced diabetic rats with A. occidentale and riboceine at the same dose significantly (p < 0.05) ameliorated hyperglycemic effects by improving hepatic and renal functions and antioxidants, preventing hepatic fat accumulation by downregulation of ACC, FAS and GFAT expression, improving β-cell functions through up-regulation of pancreatic insulin, P16NK4A, Mki-67 and pdx-1 expression. Induction of diabetes upregulated mRNA expression of KIM-1, which was ameliorated after treatment of the rats with A. occidentale and riboceine.

Conclusion

The results obtained in this study demonstrate significant antidiabetic properties of ethanolic extract of A. occidentale and riboceine.

Suppressing Inflammation for the Treatment of Diabetic Retinopathy and Age-Related Macular Degeneration: Dazdotuftide as a Potential New Multitarget Therapeutic Candidate

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are major causes of blindness globally. The primary treatment option for DME and neovascular AMD (nAMD) is anti-vascular endothelial growth factor (VEGF) compounds, but this treatment modality often yields insufficient results, and monthly injections can place a burden on the health system and patients. Although various inflammatory pathways and mediators have been recognized as key players in the development of DR and AMD, there are limited treatment options targeting these pathways. Molecular pathways that are interlinked, or triggers of multiple inflammatory pathways, could be promising targets for drug development. This review focuses on the role of inflammation in the pathogenesis of DME and AMD and presents current anti-inflammatory compounds, as well as a potential multitarget anti-inflammatory compound (dazdotuftide) that could be a candidate treatment option for the management of DME and AMD.

Glycaemic control in people with diabetes following acute myocardial infarction

Diabetes is a highly prevalent disease associated with considerable cardiovascular end organ damage and mortality. Despite significant changes to the management of acute myocardial infarction over the last two decades, people with diabetes remain at risk of complications and mortality following a myocardial infarct for a multitude of reasons, including increased coronary atherosclerosis, associated coronary microvascular dysfunction, and diabetic cardiomyopathy. Dysglycaemia causes significant endothelial dysfunction and upregulation of inflammation within the vasculature and epigenetic changes mean that these deleterious effects may persist despite subsequent efforts to tighten glycaemic control. Whilst clinical guidelines advocate for the avoidance of both hyper- and hypoglcyaemia in the peri-infarct period, the evidence base is lacking, and currently there is no consensus on the benefits of glycaemic control beyond this period. Glycaemic variability contributes to the glycaemic milieu and may have prognostic importance following myocardial infarct. The use of continuous glucose monitoring means that glucose trends and parameters can now be captured and interrogated, and its use, along with newer medicines, may provide novel opportunities for intervention after myocardial infarction in people with diabetes.

Exploring the quality markers and mechanism of Bushen Huoxue Prescription in prevention and treatment of diabetic retinopathy based on Chinmedomics strategy

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese herbal medicines have complex chemical composition; therefore, revealing the effective substances of Chinese herbal medicine becomes a prerequisite for scientific elucidation of the mechanism of action of Bushen Huoxue Prescription (BHP) against diabetic retinopathy (DR) and the development of new drugs.

AIM OF THE STUDY

The Chinmedomics technique was used to evaluate the pharmacodynamic ingredients and mechanism of action of BHP against DR rats.

MATERIALS AND METHODS

The overall physiological condition of the rats, including body weight, blood glucose, inflammatory factor levels, histological staining, and urine metabolic profile were examined to evaluate the model and its effects. The chemical composition of BHP in vivo and ex vivo was fully analyzed utilizing UPLC-Q-Exactive Orbitrap MS in conjunction with TCM serum pharmacochemistry. Finally, correlation analysis between biomarkers, and serum migration components was used to identify Quality markers (Q-markers) that were significantly associated with effectiveness.

RESULTS

The UPLC-Q-Exactive Orbitrap MS platform was used to identify a total of 29 chemicals in serum, 17 of which were highly linked with effectiveness and can be potentially employed as pharmacodynamic substances for BHP against DR. In addition, 14 biomarkers related to galactose metabolism, starch and sucrose metabolism, pantothenate and CoA biosynthesis, glycine, serine, and threonine metabolism were identified. These pathways reveal that DR may be inextricably linked to levels of oxidative stress and inflammation in the organism. Finally, five active ingredients were identified as potential Q-markers of BHP against DR, namely ajugol, protocatechuic acid, tanshinone IIA, panaxatriol and puerarin.

CONCLUSION

This study successfully clarified the efficacy and Q-markers of BHP through the Chinmedomics strategy, which is of great significance in determining the quality standards of BHP.

Regulation of peroxiredoxin-3 gene expression under basal and hyperglycemic conditions: Key roles for transcription factors Sp1, CREB and NF-κB

Peroxiredoxin-3 (Prx-3), a thioredoxin-dependent peroxidase located exclusively in the mitochondrial matrix, catalyses peroxides/peroxinitrites. Altered levels of Prx-3 is associated with diabetic cardiomyopathy (DCM). However, molecular mechanisms of Prx-3 gene regulation remain partially understood. We undertook a systemic analysis of the Prx-3 gene to identify the key motifs and transcriptional regulatory molecules. Transfection of promoter-reporter constructs in the cultured cells identified -191/+20 bp domain as the core promoter region. Stringent in silico analysis of this core promoter revealed putative binding sites for specificity protein 1 (Sp1), cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Interestingly, while co-transfection of the -191/+20 bp construct with Sp1/CREB plasmid diminished Prx3 promoter-reporter activity, mRNA and protein levels, co-transfection with NF-κB expression plasmid augmented the same. Consistently, inhibition of Sp1/CREB/NF-κB expression reversed the promoter-reporter activity, mRNA and protein levels of Prx-3, thereby confirming their regulatory effects. ChIP assays provided evidence for interactions of Sp1/CREB/NF-κB with the Prx-3 promoter. H9c2 cells treated with high glucose as well as streptozotocin (STZ)-treated diabetic rats showed time-dependent reduction in promoter activity, endogenous transcript and protein levels of Prx-3. Augmentation of Sp1/CREB protein levels and their strong binding with Prx-3 promoter are responsible for diminished Prx-3 levels under hyperglycemia. The activation/increase in the NF-κB expression under hyperglycemia was not sufficient to restore the reduction of endogenous Prx-3 levels owing to its weak binding affinity. Taken together, this study elucidates the previously unknown roles of Sp1/CREB/NF-κB in regulating Prx-3 gene expression under hyperglycemic condition.

The UDPase ENTPD5 regulates ER stress-associated renal injury by mediating protein N-glycosylation

Impaired protein N-glycosylation leads to the endoplasmic reticulum (ER) stress, which triggers adaptive survival or maladaptive apoptosis in renal tubules in diabetic kidney disease (DKD). Therapeutic strategies targeting ER stress are promising for the treatment of DKD. Here, we report a previously unappreciated role played by ENTPD5 in alleviating renal injury by mediating ER stress. We found that ENTPD5 was highly expressed in normal renal tubules; however, ENTPD5 was dynamically expressed in the kidney and closely related to pathological DKD progression in both human patients and mouse models. Overexpression of ENTPD5 relieved ER stress in renal tubular cells, leading to compensatory cell proliferation that resulted in hypertrophy, while ENTPD5 knockdown aggravated ER stress to induce cell apoptosis, leading to renal tubular atrophy and interstitial fibrosis. Mechanistically, ENTPD5-regulated N-glycosylation of proteins in the ER to promote cell proliferation in the early stage of DKD, and continuous hyperglycemia activated the hexosamine biosynthesis pathway (HBP) to increase the level of UDP-GlcNAc, which driving a feedback mechanism that inhibited transcription factor SP1 activity to downregulate ENTPD5 expression in the late stage of DKD. This study was the first to demonstrate that ENTPD5 regulated renal tubule cell numbers through adaptive proliferation or apoptosis in the kidney by modulating the protein N-glycosylation rate in the ER, suggesting that ENTPD5 drives cell fate in response to metabolic stress and is a potential therapeutic target for renal diseases.

Role of Oxidative Stress in Ocular Diseases: A Balancing Act

Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.

Diabetic Peripheral Neuropathy Associated with Foot Ulcer: One of a Kind

Significance: Diabetic peripheral neuropathy (DPN) associated with a diabetic foot ulcer (DFU) is likely to be complicated with critical factors such as biofilm infection and compromised skin barrier function of the diabetic skin. Repaired skin with a history of biofilm infection is known to be compromised in barrier function. Loss of barrier function is also observed in the oxidative stress affected diabetic and aged skin. Recent Advances: Loss of barrier function makes the skin prone to biofilm infection and cellulitis, which contributes to chronic inflammation and vasculopathy. Hyperglycemia favors biofilm formation as glucose lowering led to reduction in biofilm development. While vasculopathy limits oxygen supply, the O2 cost of inflammation is high increasing hypoxia severity. Critical Issues: The host nervous system can be inhabited by bacteria. Because electrical impulses are a part of microbial physiology, polymicrobial colonization of the host's neural circuit is likely to influence transmission of action potential. The identification of perineural apatite in diabetic patients with peripheral neuropathy suggests bacterial involvement. DPN starts in both feet at the same time. Future Directions: Pair-matched studies of DPN in the foot affected with DFU (i.e., DFU-DPN) compared with DPN in the without ulcer, and intact skin barrier function, are likely to provide critical insight that would help inform effective care strategies. This review characterizes DFU-DPN from a translational science point of view presenting a new paradigm that recognizes the current literature in the context of factors that are unique to DFU-DPN.

Antioxidant, Wound Healing Potential and In Silico Assessment of Naringin, Eicosane and Octacosane

1. Diabetic chronic wounds, mainly foot ulcers, constitute one of the most common complications of poorly managed diabetes mellitus. The most typical reasons are insufficient glycemic management, latent neuropathy, peripheral vascular disease, and neglected foot care. In addition, it is a common cause of foot osteomyelitis and amputation of the lower extremities. Patients are admitted in larger numbers attributable to chronic wounds compared to any other diabetic disease. In the United States, diabetes is currently the most common cause of non-traumatic amputations. Approximately five percent of diabetics develop foot ulcers, and one percent require amputation. Therefore, it is necessary to identify sources of lead with wound-healing properties. Redox imbalance due to excessive oxidative stress is one of the causes for the development of diabetic wounds. Antioxidants have been shown to decrease the progression of diabetic neuropathy by scavenging ROS, regenerating endogenous and exogenous antioxidants, and reversing redox imbalance. Matrix metalloproteinases (MMPs) play vital roles in numerous phases of the wound healing process. Antioxidant and fibroblast cell migration activity of Marantodes pumilum (MP) crude extract has previously been reported. Through their antioxidant, epithelialization, collagen synthesis, and fibroblast migration activities, the authors hypothesise that naringin, eicosane and octacosane identified in the MP extract may have wound-healing properties. 2. The present study aims to identify the bioactive components present in the dichloromethane (DCM) extract of M. pumilum and evaluate their antioxidant and wound healing activity. Bioactive components were identified using LCMS, HPTLC and GCMS. Excision wound on STZ-induced diabetic rat model, human dermal fibroblast (HDF) cell line and colorimetric antioxidant assays were used to evaluate wound healing and antioxidant activities, respectively. Molecular docking and pkCMS software would be utilised to predict binding energy and affinity, as well as ADME parameters. 3. Naringin (NAR), eicosane (EIC), and octacosane (OCT) present in MP displayed antioxidant action and wound excision closure. Histological examination HDF cell line demonstrates epithelialization, collagen production, fibroblast migration, polymorphonuclear leukocyte migration (PNML), and fibroblast movement. The results of molecular docking indicate a substantial attraction and contact between MMPs. pkCMS prediction indicates inadequate blood-brain barrier permeability, low toxicity, and absence of hepatotoxicity. 4. Wound healing properties of (NEO) naringin, eicosane and octacosane may be the result of their antioxidant properties and possible interactions with MMP.

Identification of stable reference genes in peripheral blood mononuclear cells from type 2 diabetes mellitus patients

Reference genes are obligatory for accurate normalization of mRNA transcript levels across samples and experimental conditions in Real Time-polymerase chain reaction (qRT-PCR) based quantitative gene expression assays. Selection of stably expressed reference genes is therefore crucial for ensuring reproducibility of such assays. However, there is a complete dearth of data on stability of commonly used reference genes in Peripheral Blood Mononuclear Cells (PBMCs) from Type 2 diabetes mellitus (T2DM) patients. We have evaluated the gene expression stability of 4 widely used reference genes (Beta-actin, ACTB; Peptidylprolyl Isomerase B, PPIB; Tyrosine 3 Monooxygenase/Tryptophan 5-Monooxygenase Activation Protein Zeta, YWHAZ; and Glyceraldehyde-3-Phosphate Dehydrogenase, GAPDH); in PBMCs from 39 T2DM patients and 47 normoglycemic (NGT) subjects. ACTB and YWHAZ were found to be the most stable genes in PBMCs from T2DM patients and therefore, can be recommended as suitable reference genes in similar contexts. GAPDH and PPIB expressions were not stable in PBMCs from T2DM patients. On using ACTB and YWHAZ as reference genes for measuring relative expression of GAPDH and PPIB in these subjects, relative GAPDH expression was found to be significantly lower in female T2DM patients, compared to female NGT subjects [GAPDH relative normalization unit (RNU): female T2DM (n = 19), median (Q1, Q3): 9.0 (8.1, 9.9); female NGT (n = 18): median (Q1, Q3): 10.1 (9.1, 11.0); P = 0.034]. Dysregulation of GAPDH in PBMCs from female T2DM patients could be associated with sex-specific differences in pathogenesis and outcomes of T2DM.

Protective Effect of Pioglitazone on Retinal Ganglion Cells in an Experimental Mouse Model of Ischemic Optic Neuropathy

The aim was to assess the protective effect of pioglitazone (PGZ) on retinal ganglion cells (RGCs) after anterior ischemic optic neuropathy (AION) in diabetic and non-diabetic mice. Adult C57BL/6 mice with induced diabetes were divided into three groups: group 1: oral PGZ (20 mg/kg) in 0.1% dimethyl sulfoxide (DMSO) for 4 weeks; group 2: oral PGZ (10 mg/kg) in 0.1% DMSO for 4 weeks; and group 3: oral DMSO only for 4 weeks (control group). Two weeks after treatment, AION was induced through photochemical thrombosis. For non-diabetic mice, adult C57BL/6 mice were divided into four groups after AION was induced: group 1: oral DMSO for 4 weeks; group 2: oral PGZ (20 mg/kg) in 0.1% DMSO for 4 weeks; group 3: oral PGZ (20 mg/kg) in 0.1% DMSO + peritoneal injection of GW9662 (one kind of PPAR-γ inhibitor) (1 mg/kg) for 4 weeks; group 4: peritoneal injection of GW9662 (1 mg/kg) for 4 weeks; One week after the induction of AION in diabetic mice, apoptosis in RGCs was much lower in group 1 (8.0 ± 4.9 cells/field) than in group 2 (24.0 ± 11.5 cells/field) and 3 (25.0 ± 7.7 cells/field). Furthermore, microglial cell infiltration in the retina (group 1: 2.0 ± 2.6 cells/field; group 2: 15.6 ± 3.5 cells/field; and group 3: 14.8 ± 7.5 cells/field) and retinal thinning (group 1: 6.7 ± 5.7 μm; group 2: 12.8 ± 6.1 μm; and group 3: 15.8 ± 5.8 μm) were also lower in group 1 than in the other two groups. In non-diabetic mice, preserved Brn3A⁺ cells were significantly greater in group 2 (2382 ± 140 Brn3A+ cells/mm², n = 7) than in group 1 (1920 ± 228 Brn3A+ cells/mm²; p = 0.03, n = 4), group 3 (1938 ± 213 Brn3A+ cells/mm²; p = 0.002, n = 4), and group 4 (2138 ± 126 Brn3A+ cells/mm²; p = 0.03, n = 4), respectively; PGZ confers protection to RGCs from damage caused by ischemic optic neuropathy in diabetic and non-diabetic mice.

Research Progress on Mitochondrial Dysfunction in Diabetic Retinopathy

Diabetic Retinopathy (DR) is one of the most important microvascular complications of diabetes mellitus, which can lead to blindness in severe cases. Mitochondria are energy-producing organelles in eukaryotic cells, which participate in metabolism and signal transduction, and regulate cell growth, differentiation, aging, and death. Metabolic changes of retinal cells and epigenetic changes of mitochondria-related genes under high glucose can lead to mitochondrial dysfunction and induce mitochondrial pathway apoptosis. In addition, mitophagy and mitochondrial dynamics also change adaptively. These mechanisms may be related to the occurrence and progression of DR, and also provide valuable clues for the prevention and treatment of DR. This article reviews the mechanism of DR induced by mitochondrial dysfunction, and the prospects for related treatment.

Crosstalk between Sirtuins and Nrf2: SIRT1 activators as emerging treatment for diabetic neuropathy

About 50% of the diabetic patients worldwide suffer from Diabetic peripheral neuropathy (DPN) which is characterized by chronic pain and loss of sensation, frequent foot ulcerations, and risk for amputation. Numerous factors like hyperglycemia, oxidative stress (OS), impaired glucose signaling, inflammatory responses, neuronal cell death are known to be the various mechanisms underlying DACD and DPN. Development of tolerance, insufficient and inadequate relief and potential toxicity of classical antinociceptives still remains a challenge in the clinical setting. Therefore, there is an emerging need for novel treatments which are both without any potential side effects as well as which focus more on the pathophysiological mechanisms underlying the disease. Also, sirtuins are known to deacetylate Nrf2 and contribute to its action of reducing ROS by generation of anti-oxidant enzymes. Therefore, targeting sirtuins could be a favourable therapeutic strategy to treat diabetic neuropathy by reducing ROS and thereby alleviating OS in DPN. In the present review, we outline the potential use of SIRT1 activators as therapeutic alternatives in treating DPN. We have tried to highlight how sirtuins are interlinked with Nrf2 and NF-κB and put forth how SIRT activators could serve as potential therapy for DPN.

Biochemical and clinical markers of endothelial dysfunction do not outweigh traditional risk factors for the presence of diabetic retinopathy in patients with type 1 diabetes

BACKGROUND

This study aimed to evaluate whether soluble vascular cytoadhesive molecule-1 (sVCAM-1), intracellular cytoadhesive molecule-1 (sICAM-1), and endothelial function as assessed by EndoPat outweighed traditional risk factors for the presence of diabetic retinopathy (DR) in patients with type 1 diabetes (T1D).

METHODS

Patients aged ≥ 12 years completed a clinical-epidemiological questionnaire. Fasting venous blood samples were obtained (lipid profile, glycemic control, and C-reactive protein levels). Vascular reactivity was assessed via peripheral arterial tonometry performed by supplying the reactive hyperemia index (RHI) through the EndoPAT device. sVCAM-1 and sICAM-1 levels were measured using multiplex assays.

RESULTS

Data were obtained from 187 patients (51.3% female), aged 32 ± 13 years with a disease duration of 14 (6-15) years and mean hemoglobin A1c (HbA1c) of 9.1% ± 2.1%. After adjustments were made, age, HbA1c, arterial blood pressure, and use of drugs that could interfere with endothelial function were found to be associated with DR. No association was noted with sVCAM-1 and sICAM-1 levels and RHI.

CONCLUSIONS

In our sample, sVCAM-1, sICAM and EndoPAT did not outweigh the traditional DR risk factors, such as age, high HbA1c, arterial blood pressure, and use of drugs that could interfere with endothelial function and are significantly associated with DR. Further prospective studies should evaluate if markers of endothelial dysfunction could predict diabetes-related micro and macrovascular complications in T1D.

Profile of crosstalk between glucose and lipid metabolic disturbance and diabetic cardiomyopathy: Inflammation and oxidative stress

In recent years, the risk, such as hypertension, obesity and diabetes mellitus, of cardiovascular diseases has been increasing explosively with the development of living conditions and the expansion of social psychological pressure. The disturbance of glucose and lipid metabolism contributes to both collapse of myocardial structure and cardiac dysfunction, which ultimately leads to diabetic cardiomyopathy. The pathogenesis of diabetic cardiomyopathy is multifactorial, including inflammatory cascade activation, oxidative/nitrative stress, and the following impaired Ca2+ handling induced by insulin resistance/hyperinsulinemia, hyperglycemia, hyperlipidemia in diabetes. Some key alterations of cellular signaling network, such as translocation of CD36 to sarcolemma, activation of NLRP3 inflammasome, up-regulation of AGE/RAGE system, and disequilibrium of micro-RNA, mediate diabetic oxidative stress/inflammation related myocardial remodeling and ventricular dysfunction in the context of glucose and lipid metabolic disturbance. Here, we summarized the detailed oxidative stress/inflammation network by which the abnormality of glucose and lipid metabolism facilitates diabetic cardiomyopathy.

Modelling Diabetic Cardiomyopathy: Using Human Stem Cell-Derived Cardiomyocytes to Complement Animal Models

Diabetes is a global epidemic, with cardiovascular disease being the leading cause of death in diabetic patients. There is a pressing need for an in vitro model to aid understanding of the mechanisms driving diabetic heart disease, and to provide an accurate, reliable tool for drug testing. Human induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have potential as a disease modelling tool. There are several factors that drive molecular changes inside cardiomyocytes contributing to diabetic cardiomyopathy, including hyperglycaemia, lipotoxicity and hyperinsulinemia. Here we discuss these factors and how they can be seen in animal models and utilised in cell culture to mimic the diabetic heart. The use of human iPSC-CMs will allow for a greater understanding of disease pathogenesis and open up new avenues for drug testing.

O-GlcNAc Modification and Its Role in Diabetic Retinopathy

Diabetic retinopathy (DR) is a leading complication in type 1 and type 2 diabetes and has emerged as a significant health problem. Currently, there are no effective therapeutic strategies owing to its inconspicuous early lesions and complex pathological mechanisms. Therefore, the mechanism of molecular pathogenesis requires further elucidation to identify potential targets that can aid in the prevention of DR. As a type of protein translational modification, O-linked β-N-acetylglucosamine (O-GlcNAc) modification is involved in many diseases, and increasing evidence suggests that dysregulated O-GlcNAc modification is associated with DR. The present review discusses O-GlcNAc modification and its molecular mechanisms involved in DR. O-GlcNAc modification might represent a novel alternative therapeutic target for DR in the future.

Impact of SGLT2 inhibitors on the kidney in people with type 2 diabetes and severely increased albuminuria

INTRODUCTION

Diabetes is the most common cause of end stage kidney disease. Therapies such as sodium-glucose co-transporter-2 inhibitors have been identified over the last decade as effective oral hypoglycemic agents that also confer additional cardio and kidney protection. Knowledge of their mechanism of action and impact on patients with diabetes and albuminuria is vital in galvanizing prescriber confidence and increasing clinical uptake.

AREAS COVERED

This manuscript discusses the pathophysiology of diabetic kidney disease, patho-physiological mechanisms for sodium-glucose co-transporter-2 inhibitors, and their impact on patients with Type 2 diabetes mellitus and albuminuric kidney disease.

EXPERT OPINION

Sodium-glucose co-transporter-2 inhibitors reduce albuminuria with consequent benefits on cardiovascular and kidney outcomes in patients with diabetes and severe albuminuria. Whilst they have been incorporated into guidelines, the uptake of these agents into clinical practice has been slow. Increasing the uptake of these agents into clinical practice is necessary to improve outcomes for the large number of patients with diabetic kidney disease globally.

Pathogenesis of Distal Symmetrical Polyneuropathy in Diabetes

Distal symmetrical polyneuropathy (DSPN) is a serious complication of diabetes associated with significant disability and mortality. Although more than 50% of people with diabetes develop DSPN, its pathogenesis is still relatively unknown. This lack of understanding has limited the development of novel disease-modifying therapies and left the reasons for failed therapies uncertain, which is critical given that current management strategies often fail to achieve long-term efficacy. In this article, the pathogenesis of DSPN is reviewed, covering pathogenic changes in the peripheral nervous system, microvasculature and central nervous system (CNS). Furthermore, the successes and limitations of current therapies are discussed, and potential therapeutic targets are proposed. Recent findings on its pathogenesis have called the definition of DSPN into question and transformed the disease model, paving the way for new research prospects.

Implications of Diabetes-Induced Altered Metabolites on Retinal Neurodegeneration

Diabetic retinopathy (DR) is one of the major complications of diabetic eye diseases, causing vision loss and blindness worldwide. The concept of diabetic retinopathy has evolved from microvascular disease into more complex neurovascular disorders. Early in the disease progression of diabetes, the neuronal and glial cells are compromised before any microvascular abnormalities clinically detected by the ophthalmoscopic examination. This implies understanding the pathophysiological mechanisms at the early stage of disease progression especially due to diabetes-induced metabolic alterations to damage the neural retina so that early intervention and treatments options can be identified to prevent and inhibit the progression of DR. Hyperglycemia has been widely considered the major contributor to the progression of the retinal damage, even though tight control of glucose does not seem to have a bigger effect on the incidence or progression of retinal damage that leads to DR. Emerging evidence suggests that besides diabetes-induced hyperglycemia, dyslipidemia and amino acid defects might be a major contributor to the progression of early neurovascular retinal damage. In this review, we have discussed recent advances in the alterations of key metabolites of carbohydrate, lipid, and amino acids and their implications for neurovascular damage in DR.

Abnormal urinary loss of vitamin C in diabetes: prevalence and clinical characteristics of a vitamin C renal leak

BACKGROUND

Diabetes is associated with low plasma vitamin C concentrations.

OBJECTIVES

We investigated the contribution of dysregulated vitamin C renal physiology, its prevalence, and associated clinical characteristics.

METHODS

An essential prerequisite was determination of normal vitamin C renal threshold, the plasma concentration at which vitamin C first appears in urine. Using data from 17 healthy participants who underwent vitamin C depletion-repletion studies with a vitamin C dose range of 15-1250 mg daily, renal threshold was estimated using physiology-based pharmacokinetics modeling. Applying renal threshold 95% CIs, we estimated the minimal elimination threshold, the plasma concentration below which no vitamin C was expected in urine of healthy people. Renal leak was defined as abnormal presence of vitamin C in urine with plasma concentrations below the minimal elimination threshold. Criteria were tested in a cross-sectional cohort study of individuals with diabetes (82) and nondiabetic controls (80) using matched plasma and urine samples.

RESULTS

Vitamin C renal thresholds in healthy men and women were [mean (SD)] 48.5 (5.2) µM and 58.3 (7.5) µM, respectively. Compared with nondiabetic controls, participants with diabetes had significantly higher prevalence of vitamin C renal leak (9% compared with 33%; OR: 5.07; 95% CI: 1.97, 14.83; P < 0.001) and 30% lower mean plasma vitamin C concentrations (53.1 µM compared with 40.9 µM, P < 0.001). Fasting plasma glucose, glycosylated hemoglobin A1c, BMI, micro/macrovascular complications, and protein/creatinine ratio were predictive of vitamin C renal leak.

CONCLUSIONS

Increased prevalence of vitamin C renal leak in diabetes is associated with reduced plasma vitamin C concentrations. Glycemic control, microvascular complications, obesity, and proteinuria are predictive of renal leak.

The Role of Mitochondria in Metabolic Syndrome–Associated Cardiomyopathy

With the rapid development of society, the incidence of metabolic syndrome (MS) is increasing rapidly. Evidence indicated that patients diagnosed with MS usually suffered from cardiomyopathy, called metabolic syndrome–associated cardiomyopathy (MSC). The clinical characteristics of MSC included cardiac hypertrophy and diastolic dysfunction, followed by heart failure. Despite many studies on this topic, the detailed mechanisms are not clear yet. As the center of cellular metabolism, mitochondria are crucial for maintaining heart function, while mitochondria dysfunction plays a vital role through mechanisms such as mitochondrial energy deprivation, calcium disorder, and ROS (reactive oxygen species) imbalance during the development of MSC. Accordingly, in this review, we will summarize the characteristics of MSC and especially focus on the mechanisms related to mitochondria. In addition, we will update new therapeutic strategies in this field.

Polyol pathway and redox balance in diabetes

Diabetes is a major public health disease that is globally approaching epidemic proportions. One of the major causes of type 2 diabetes is either a defect in insulin secretion or insulin action which is usually caused by a combination of genetic and environmental factors. Not only these factors but others such as deregulation of various pathways, and oxidative stress are also known to trigger the redox imbalance in diabetics. Increasing evidences suggest that there are tight interactions between the development of diabetes and redox imbalance. An alternate pathway of glucose metabolism, the polyol pathway, becomes active in patients with diabetes that disturbs the balance between NADH and NAD+ . The occurrence of such redox imbalance supports other pathways that lead to oxidative damage to DNA, lipids, and proteins and consequently to oxidative stress which further ascend diabetes and its complications. However, the precise mechanism through which oxidative stress regulates diabetes progression remains to be elucidated. The understanding of how antioxidants and oxidants are controlled and impact the generation of oxidative stress and progression of diabetes is essential. The main focus of this review is to provide an overview of redox imbalance caused by oxidative stress through the polyol pathway. Understanding the pathological role of oxidative stress in diabetes will help to design potential therapeutic strategies against diabetes.

Mechanistic approach towards diabetic neuropathy screening techniques and future challenges: A review

Diabetic neuropathy, also called peripheral diabetic neuropathy (PDN), is among the most significant diabetes health consequences, alongside diabetic nephropathy, diabetic cardiomyopathy and diabetic retinopathy. Diabetic neuropathy is the existence of signs and indications of peripheral nerve damage in patients with diabetes after other causes have been governed out. Diabetic neuropathy is a painful and severe complication of diabetes that affects roughly 20% of people. The development of diabetic neuropathy is regulated by blood arteries that nourish the peripheral nerves and metabolic problems such as increased stimulation of polyol pathway, loss of myo-inositol and enhanced non-enzymatic glycation. It's divided into four types based on where neurons are most affected: autonomic, peripheral, proximal, and focal, with each kind presenting different symptoms like numbing, gastrointestinal disorders, and heart concerns. Pharmacotherapy for neuropathic pain is complex and for many patients, effective treatment is lacking; as a result, scientific proof recommendations are crucial. As a result, the current demand is to give the most vital medications or combinations of drugs that work directly on the nerves to help diabetic neuropathy patients feel less pain without causing any adverse effects. In diabetic neuropathy research, animal models are ubiquitous, with rats and mice being the most typically chosen for various reasons. This review covers the epidemiology, clinical features, pathology, clinical symptom, mechanism of diabetic neuropathy development, diagnosis, screening models of animals, diabetic neuropathy pharmacotherapy.

Therapeutic potential of vitamin B1 derivative benfotiamine from diabetes to COVID-19

Benfotiamine (S-benzoylthiamine-O-monophosphate), a unique, lipid-soluble derivative of thiamine, is the most potent allithiamine found in roasted garlic, as well as in other herbs of the genus Allium. In addition to potent antioxidative properties, benfotiamine has also been shown to be a strong anti-inflammatory agent with therapeutic significance to several pathological complications. Specifically, over the past decade or so, benfotiamine has been shown to prevent not only various secondary diabetic complications but also several inflammatory complications such as uveitis and endotoxemia. Recent studies also demonstrate that this compound could be used to prevent the symptoms associated with various infectious diseases such as HIV and COVID-19. In this review article, the authors discuss the significance of benfotiamine in the prevention of various pathological complications.

Effect of Aucubin-Containing Eye Drops on Tear Hyposecretion and Lacrimal Gland Damage Induced by Urban Particulate Matter in Rats

Exposure to particulate matter is a causative factor of dry eye disease. We aimed to investigate the beneficial effect of eye drops containing aucubin on dry eye disease induced by urban particulate matter (UPM). Dry eye was induced in male SD rats (6 weeks old) by topical exposure to UPM thrice a day for 5 d. Eye drops containing 0.1% aucubin or 0.5% aucubin were topically administered directly into the eye after UPM exposure for an additional 5 d. Tear secretion was evaluated using a phenol red thread tear test and corneal irregularity. The oxidative damage in the lacrimal gland was evaluated using TUNEL and immunohistochemical staining. The topical administration of aucubin significantly attenuated UPM-induced tear hyposecretion (control group: 9.25 ± 0.62 mm, UPM group: 4.55 ± 0.25 mm, 0.1% aucubin: 7.12 ± 0.58 mm, and 0.5% aucubin: 7.88 ± 0.75 mm) and corneal irregularity (control group: 0.00 ± 0.00, UPM group: 3.40 ± 0.29, 0.1% aucubin: 1.80 ± 0.27, and 0.5% aucubin: 1.15 ± 0.27). In addition, aucubin also reduced the UPM-induced apoptotic injury of lacrimal gland cells induced by oxidative stress through the increased expression of HMGB1 and RAGE. These findings indicate that the topical administration of aucubin eye drops showed a beneficial effect against UPM-induced abnormal ocular changes, such as tear hyposecretion and lacrimal gland damage. Therefore, our results reveal the pharmacological activities of aucubin in dry eye disease.

Treadmill running increases the calcium sensitivity of myofilaments in diabetic rats

The cardiovascular benefits of regular exercise are unequivocal, yet patients with type 2 diabetes respond poorly to exercise due to a reduced cardiac reserve. The contractile response of diabetic cardiomyocytes to beta-adrenergic stimulation is attenuated, which may result in altered myofilament calcium sensitivity and post-translational modifications of cardiac troponin I (cTnI). Treadmill running increases myofilament calcium sensitivity in non‑diabetic rats, and thus we hypothesized that endurance training would increase calcium sensitivity of diabetic cardiomyocytes and alter site-specific phosphorylation of cTnI. Calcium sensitivity, or pCa₅₀, was measured in Zucker Diabetic Fatty (ZDF) non-diabetic (nDM) and diabetic (DM) rat hearts after 8 weeks of either a sedentary (SED) or progressive treadmill running (TR) intervention. Skinned cardiomyocytes were connected to a capacitance-gauge transducer and a torque motor to measure force as a function of pCa (‑log[Ca²⁺]). Specific phospho-sites on cTnI and O‑GlcNAcylation were quantified by immunoblot and total protein phosphorylation by fluorescent gel staining (ProQ Diamond). The novel finding in this study was that training increased pCa₅₀ in both DM and nDM cardiomyocytes (p = 0.009). Phosphorylation of cTnI amino acid residues Ser23/24, a crucial protein kinase A site, and Threonine (Thr)144, was lower in DM hearts, but there was no effect of training on site-specific phosphorylation. Additionally, total phosphorylation and O-GlcNAcylation levels were not different between SED and TR groups. These findings suggest that regular exercise may benefit the diabetic heart by specifically targeting myofilament contractile function.

Biochemical mechanism underlying the pathogenesis of diabetic retinopathy and other diabetic complications in humans: the methanol-formaldehyde-formic acid hypothesis

Hyperglycemia in diabetic patients is associated with abnormally-elevated cellular glucose levels. It is hypothesized that increased cellular glucose will lead to increased formation of endogenous methanol and/or formaldehyde, both of which are then metabolically converted to formic acid. These one-carbon metabolites are known to be present naturally in humans, and their levels are increased under diabetic conditions. Mechanistically, while formaldehyde is a cross-linking agent capable of causing extensive cytotoxicity, formic acid is an inhibitor of mitochondrial cytochrome oxidase, capable of inducing histotoxic hypoxia, ATP deficiency and cytotoxicity. Chronic increase in the production and accumulation of these toxic one-carbon metabolites in diabetic patients can drive the pathogenesis of ocular as well as other diabetic complications. This hypothesis is supported by a large body of experimental and clinical observations scattered in the literature. For instance, methanol is known to have organ- and species-selective toxicities, including the characteristic ocular lesions commonly seen in humans and non-human primates, but not in rodents. Similarly, some of the diabetic complications (such as ocular lesions) also have a characteristic species-selective pattern, closely resembling methanol intoxication. Moreover, while alcohol consumption or combined use of folic acid plus vitamin B is beneficial for mitigating acute methanol toxicity in humans, their use also improves the outcomes of diabetic complications. In addition, there is also a large body of evidence from biochemical and cellular studies. Together, there is considerable experimental support for the proposed hypothesis that increased metabolic formation of toxic one-carbon metabolites in diabetic patients contributes importantly to the development of various clinical complications.

Role of Oxidative Stress in Diabetic Cardiomyopathy

Type 2 diabetes is a redox disease. Oxidative stress and chronic inflammation induce a switch of metabolic homeostatic set points, leading to glucose intolerance. Several diabetes-specific mechanisms contribute to prominent oxidative distress in the heart, resulting in the development of diabetic cardiomyopathy. Mitochondrial overproduction of reactive oxygen species in diabetic subjects is not only caused by intracellular hyperglycemia in the microvasculature but is also the result of increased fatty oxidation and lipotoxicity in cardiomyocytes. Mitochondrial overproduction of superoxide anion radicals induces, via inhibition of glyceraldehyde 3-phosphate dehydrogenase, an increased polyol pathway flux, increased formation of advanced glycation end-products (AGE) and activation of the receptor for AGE (RAGE), activation of protein kinase C isoforms, and an increased hexosamine pathway flux. These pathways not only directly contribute to diabetic cardiomyopathy but are themselves a source of additional reactive oxygen species. Reactive oxygen species and oxidative distress lead to cell dysfunction and cellular injury not only via protein oxidation, lipid peroxidation, DNA damage, and oxidative changes in microRNAs but also via activation of stress-sensitive pathways and redox regulation. Investigations in animal models of diabetic cardiomyopathy have consistently demonstrated that increased expression of the primary antioxidant enzymes attenuates myocardial pathology and improves cardiac function.

Blockage of MLKL prevents myelin damage in experimental diabetic neuropathy

Diabetic neuropathy is a commonly occurring complication of diabetes that affects hundreds of millions of patients worldwide. Patients suffering from diabetic neuropathy experience abnormal sensations and have damage in their peripheral nerve axons as well as myelin, a tightly packed Schwann cell sheath that wraps around axons to provide insulation and increases electrical conductivity along the nerve fibers. The molecular events underlying myelin damage in diabetic neuropathy are largely unknown, and there is no efficacious treatment for the disease. The current study, using a diabetic mouse model and human patient nerve samples, uncovered a molecular mechanism underlying myelin sheath damage in diabetic neuropathy and provides a potential treatment strategy for the disease.

Demyelination is a pathological feature of diabetic neuropathy, a common and painful complication of diabetes, yet the mechanisms underlying diabetes-induced demyelination remain unclear. Here, we show that targeting mixed lineage kinase domain–like protein (MLKL), a protein critical in necroptosis, using Schwann cell–specific genetic knockout, S441A single–amino acid knockin mutation, or pharmacological inhibition all blocked myelin sheath decompaction and prevented the decrease of nerve conduction velocity in streptozotocin-induced diabetic mice. The decompaction of the myelin sheaths of sural nerves was observed in biopsy samples from diabetic patients, and the MLKL-mediated myelin breakdown was activated in human diabetic neuropathy patients. Our study establishes a direct myelin degradation–related role for MLKL in diabetic neuropathy and defines MLKL as a druggable target for developing agents to prevent or treat diabetic neuropathy.

Lycopene: A Potent Antioxidant for the Amelioration of Type II Diabetes Mellitus

Nutrition is of utmost importance in chronic disease management and has often been described as the cornerstone of a variety of non-communicable diseases. In particular, type II diabetes mellitus (T2DM) represents a prevalent and global public health crisis. Lycopene, a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and vegetables, has been extensively studied for its biological activities and treatment efficiency in diabetes care. Epidemiological investigations indicate that lycopene has potential antioxidant properties, is capable of scavenging reactive species, and alleviates oxidative stress in T2DM patients. This review aims to summarize the characteristics and mechanisms of action of lycopene as a potent antioxidant for T2DM. In addition, the evidence demonstrating the effects of lycopene on glycemic control and oxidative stress biomarkers in T2DM are also highlighted using animal and human studies as literature approach.

Demystifying the O-GlcNAc Code: A Systems View

Post-translational modification with O-linked β-N-acetylglucosamine (O-GlcNAc), a process referred to as O-GlcNAcylation, occurs on a vast variety of proteins. Mounting evidence in the past several decades has clearly demonstrated that O-GlcNAcylation is a unique and ubiquitous modification. Reminiscent of a code, protein O-GlcNAcylation functions as a crucial regulator of nearly all cellular processes studied. The primary aim of this review is to summarize the developments in our understanding of myriad protein substrates modified by O-GlcNAcylation from a systems perspective. Specifically, we provide a comprehensive survey of O-GlcNAcylation in multiple species studied, including eukaryotes (e.g., protists, fungi, plants, Caenorhabditis elegans, Drosophila melanogaster, murine, and human), prokaryotes, and some viruses. We evaluate features (e.g., structural properties and sequence motifs) of O-GlcNAc modification on proteins across species. Given that O-GlcNAcylation functions in a species-, tissue-/cell-, protein-, and site-specific manner, we discuss the functional roles of O-GlcNAcylation on human proteins. We focus particularly on several classes of relatively well-characterized human proteins (including transcription factors, protein kinases, protein phosphatases, and E3 ubiquitin-ligases), with representative O-GlcNAc site-specific functions presented. We hope the systems view of the great endeavor in the past 35 years will help demystify the O-GlcNAc code and lead to more fascinating studies in the years to come.

Molecular mechanisms of coronary microvascular endothelial dysfunction in diabetes mellitus: focus on mitochondrial quality surveillance

Coronary microvascular endothelial dysfunction is both a culprit and a victim of diabetes, and can accelerate diabetes-related microvascular and macrovascular complications by promoting vasoconstrictive, pro-inflammatory and pro-thrombotic responses. Perturbed mitochondrial function induces oxidative stress, disrupts metabolism and activates apoptosis in endothelial cells, thus exacerbating the progression of coronary microvascular complications in diabetes. The mitochondrial quality surveillance (MQS) system responds to stress by altering mitochondrial metabolism, dynamics (fission and fusion), mitophagy and biogenesis. Dysfunctional mitochondria are prone to fission, which generates two distinct types of mitochondria: one with a normal and the other with a depolarized mitochondrial membrane potential. Mitochondrial fusion and mitophagy can restore the membrane potential and homeostasis of defective mitochondrial fragments. Mitophagy-induced decreases in the mitochondrial population can be reversed by mitochondrial biogenesis. MQS abnormalities induce pathological mitochondrial fission, delayed mitophagy, impaired metabolism and defective biogenesis, thus promoting the accumulation of unhealthy mitochondria and the activation of mitochondria-dependent apoptosis. In this review, we examine the effects of MQS on mitochondrial fitness and explore the association of MQS disorders with coronary microvascular endothelial dysfunction in diabetes. We also discuss the potential to treat diabetes-related coronary microvascular endothelial dysfunction using novel MQS-altering drugs.

Propofol protects against high glucose-mediated endothelial injury via inhibition of COX2 and iNOS expressions

Perioperative hyperglycemia is a common metabolic disorder in the clinic. Hyperglycemia, via upregulation of E74-like ETS transcription factor 3 (ELF3), induces cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS) expressions, thus leading to endothelial apoptosis and vascular endothelial injury. Propofol is a widely used anesthetic. In the present study, we explored whether and how propofol protects against high glucose-induced COX2 and iNOS expressions in human umbilical vein endothelial cells (HUVECs). We found that high glucose level decreases cell viability and increases COX2 and iNOS expressions in HUVECs. Our data also indicated that ELF3 overexpression participates in high glucose-mediated cell viability reduction and high glucose-induced COX2 and iNOS expressions. Moreover, propofol treatment improves high glucose-mediated reduction in cell viability and decreases COX2 and iNOS expressions via inhibition of ELF3 expressions. Furthermore, specificity protein 1 (SP1) was found to regulate ELF3 expression, thus mediating endothelial injury. Propofol inhibits high glucose-induced SP1 expression. High glucose increases the abundance of SP1 bound to the ELF3 promoter, which can be reversed by propofol treatment. The protective effect of propofol is reversed by SP1 overexpression. In conclusion, propofol downregulates high glucose-induced SP1 expression, thus attenuating high glucose-induced ELF3 expression, inhibiting high glucose-induced COX2 and iNOS expressions, and improving high glucose-mediated cell viability reduction in HUVECs.

Recent developments of neuroprotective agents for degenerative retinal disorders

Retinal degeneration is a debilitating ocular complication characterized by the progressive loss of photoreceptors and other retinal neurons, which are caused by a group of retinal diseases affecting various age groups, and increasingly prevalent in the elderly. Age-related macular degeneration, diabetic retinopathy and glaucoma are among the most common complex degenerative retinal disorders, posing significant public health problems worldwide largely due to the aging society and the lack of effective therapeutics. Whilst pathoetiologies vary, if left untreated, loss of retinal neurons can result in an acquired degeneration and ultimately severe visual impairment. Irrespective of underlined etiology, loss of neurons and supporting cells including retinal pigment epithelium, microvascular endothelium, and glia, converges as the common endpoint of retinal degeneration and therefore discovery or repurposing of therapies to protect retinal neurons directly or indirectly are under intensive investigation. This review overviews recent developments of potential neuroprotectants including neuropeptides, exosomes, mitochondrial-derived peptides, complement inhibitors, senolytics, autophagy enhancers and antioxidants either still experimentally or in clinical trials. Effective treatments that possess direct or indirect neuroprotective properties would significantly lift the burden of visual handicap.

New horizons of biomaterials in treatment of nerve damage in diabetes mellitus: A translational prospective review

BACKGROUND

Peripheral nerve injury is a serious concern that leads to loss of neuronal communication that impairs the quality of life and, in adverse conditions, causes permanent disability. The limited availability of autografts with associated demerits shifts the paradigm of researchers to use biomaterials as an alternative treatment approach to recover nerve damage.

PURPOSE

The purpose of this study is to explore the role of biomaterials in translational treatment approaches in diabetic neuropathy.

STUDY DESIGN

The present study is a prospective review study.

METHODS

Published literature on the role of biomaterials in therapeutics was searched for.

RESULTS

Biomaterials can be implemented with desired characteristics to overcome the problem of nerve regeneration. Biomaterials can be further exploited in the treatment of nerve damage especially associated with PDN. These can be modified, customized, and engineered as scaffolds with the potential of mimicking the extracellular matrix of nerve tissue along with axonal regeneration. Due to their beneficial biological deeds, they can expedite tissue repair and serve as carriers of cellular and pharmacological treatments. Therefore, the emerging research area of biomaterials-mediated treatment of nerve damage provides opportunities to explore them as translational biomedical treatment approaches.

CONCLUSIONS

Pre-clinical and clinical trials in this direction are needed to establish the effective role of several biomaterials in the treatment of other human diseases.

Oxidative stress-mediated beta cell death and dysfunction as a target for diabetes management

The biggest drawback of a current diabetes therapy is the treatment of the consequences not the cause of the disease. Regardless of the diabetes type, preservation and recovery of functional pancreatic beta cells stands as the biggest challenge in the treatment of diabetes. Free radicals and oxidative stress are among the major mediators of autoimmune destruction of beta cells in type 1 diabetes (T1D) or beta cell malfunction and death provoked by glucotoxicity and insulin resistance in type 2 diabetes (T2D). Additionally, oxidative stress reduces functionality of beta cells in T2D by stimulating their de-/trans-differentiation through the loss of transcription factors critical for beta cell development, maturity and regeneration. This review summarizes up to date clarified redox-related mechanisms involved in regulating beta cell identity and death, underlining similarities and differences between T1D and T2D. The protective effects of natural antioxidants on the oxidative stress-induced beta cell failure were also discussed. Considering that oxidative stress affects epigenetic regulatory mechanisms involved in the regulation of pancreatic beta cell survival and insulin secretion, this review highlighted huge potential of epigenetic therapy. Special attention was paid on application of the state-of-the-art CRISPR/Cas9 technology, based on targeted epigenome editing with the purpose of changing the differentiation state of different cell types, making them insulin-producing with ability to attenuate diabetes. Clarification of the above-mentioned mechanisms could provide better insight into diabetes etiology and pathogenesis, which would allow development of novel, potentially more efficient therapeutic strategies for the prevention or reversion of beta cell loss.

Research Progress of circRNAs in Inflammatory Mechanisms of Diabetic Retinopathy: An Emerging Star with Potential Therapeutic Targets

PURPOSE

 We summarized the existing studies to elaborate the biogenesis and function of circRNAs, the effect of aberrant circRNAs expression in the mechanism of inflammation and diabetic retinopathy (DR) respectively and further explored the vital roles of circRNAs in inflammation involved in DR. Methods: We conducted a systematical literature search of abundant electronic databases (PubMed, GeneMedical and MEDLINE) up to August 2021. Results: In this review, we exhibited the biogenesis and function of circRNAs and highlighted the components of inflammatory mediators implicated in DR. Numerous circRNAs, such as circHIPK3, circZNF609, circRNA_0084043, circ_0002570, circ_0041795, circEhmt1 and circ-ITCH were discovered to play vital roles in inflammation involved in DR, which provided new ideas for diagnosis and treatment of DR. Moreover, we proposed not only the epigenetic functions of circRNAs but also novel forms of the inflammatory response, including pyroptosis, to inspire further exploration and creative research in this field. Conclusion: CircRNAs were implicated in the progression and development of inflammation in DR via aberrant expression and modulation of gene expression, serving as an emerging star with potential therapeutic targets.

Polydatin Alleviates Diabetes-Induced Hyposalivation through Anti-Glycation Activity in db/db Mouse

Polydatin (resveratrol-3-O-β-mono-D-glucoside) is a polyphenol that can be easily accessed from peanuts, grapes, and red wine, and is known to have antiglycation, antioxidant, and anti-inflammatory effects. Diabetes mellitus is a very common disease, and diabetic complications are very common complications. The dry mouth symptom is one of the most common oral complaints in patients with diabetes mellitus. Diabetes mellitus is thought to promote hyposalivation. In this study, we aimed to investigate the improvement effect of polydatin on diabetes-induced hyposalivation in db/db mouse model of type 2 diabetes. We examined salivary flow rate, TUNEL assay, PAS staining, and immunohistochemical staining for AGEs, RAGE, HMGB1, 8-OHdG, and AQP5 to evaluate the efficacy of polydatin in the submandibular salivary gland. Diabetic db/db mice had a decreased salivary flow rate and salivary gland weight. The salivary gland of the vehicle-treated db/db mice showed an increased apoptotic cell injury. The AGEs were highly accumulated, and its receptor, RAGE expression was also enhanced. Expressions of HMGB1, an oxidative cell damage marker, and 8-OHdG, an oxidative DNA damage marker, increased greatly. However, polydatin ameliorated this hypofunction of the salivary gland and inhibited diabetes-related salivary cell injury. Furthermore, polydatin improved mucin accumulation, which is used as a damage marker for salivary gland acinar cells, and decreased expression of water channel AQP5 was improved by polydatin. In conclusion, polydatin has a potent protective effect on diabetes-related salivary gland hypofunction through its antioxidant and anti-glycation activities, and its AQP5 upregulation. This result suggests the possibility of the use of polydatin as a therapeutic drug to improve hyposalivation caused by diabetes.

Quercetin for managing type 2 diabetes and its complications, an insight into multitarget therapy

BACKGROUND

Quercetin, a bioflavonoid abundant in grapefruit, onion, berries, etc., has vast therapeutic potential, especially against Type 2 diabetes and its complications. Quercetin showed similar effects as that of metformin, (widely prescribed antidiabetic drug) in cell lines models (Sajan et al., 2010; Dhanya et al., 2017). In vivo findings also showcase it as a promising agent against diabetes and its pathophysiological complications.

SCOPE AND APPROACH

Quercetin can be produced on a large scale through a novel fermentation-based glycosylation strategy from cheap substrates and can be utilized as a dietary supplement. The review focuses on the mounting evidence pointing to Quercetin as a promising candidate for managing type 2 diabetes and its oxidative stress mediated pathophysiological complications.

CONCLUSION

Quercetin acts on multiple targets of diabetes and regulates key signalling pathways which improve the symptoms as well as the complications of Type 2 diabetes. However further studies are needed to improve the bioavailability and to establish a dosing regimen for Quercetin.

An Overview of Glycosylation and its Impact on Cardiovascular Health and Disease

The cardiovascular system is a complex and well-organized system in which glycosylation plays a vital role. The heart and vascular wall cells are constituted by an array of specific receptors; most of them are N- glycosylated and mucin-type O-glycosylated. There are also intracellular signaling pathways regulated by different post-translational modifications, including O-GlcNAcylation, which promote adequate responses to extracellular stimuli and signaling transduction. Herein, we provide an overview of N-glycosylation and O-glycosylation, including O-GlcNAcylation, and their role at different levels such as reception of signal, signal transduction, and exogenous molecules or agonists, which stimulate the heart and vascular wall cells with effects in different conditions, like the physiological status, ischemia/reperfusion, exercise, or during low-grade inflammation in diabetes and aging. Furthermore, mutations of glycosyltransferases and receptors are associated with development of cardiovascular diseases. The knowledge on glycosylation and its effects could be considered biochemical markers and might be useful as a therapeutic tool to control cardiovascular diseases.

The Fate Status of Stem Cells in Diabetes and its Role in the Occurrence of Diabetic Complications

Diabetes mellitus (DM) is becoming a growing risk factor for public health worldwide. It is a very common disease and is widely known for its susceptibility to multiple complications which do great harm to the life and health of patients, some even lead to death. To date, there are many mechanisms for the complications of diabetes, including the generation of reactive oxygen species (ROS) and the abnormal changes of gas transmitters, which ultimately lead to injuries of cells, tissues and organs. Normally, even if injured, the body can quickly repair and maintain its homeostasis. This is closely associated with the repair and regeneration ability of stem cells. However, many studies have demonstrated that stem cells happen to be damaged under DM, which may be a nonnegligible factor in the occurrence and progression of diabetic complications. Therefore, this review summarizes how diabetes causes the corresponding complications by affecting stem cells from two aspects: stem cells dysfunctions and stem cells quantity alteration. In addition, since mesenchymal stem cells (MSCs), especially bone marrow mesenchymal stem cells (BMMSCs), have the advantages of strong differentiation ability, large quantity and wide application, we mainly focus on the impact of diabetes on them. The review also puts forward the basis of using exogenous stem cells to treat diabetic complications. It is hoped that through this review, researchers can have a clearer understanding of the roles of stem cells in diabetic complications, thus promoting the process of using stem cells to treat diabetic complications.

Protective role of vitamin D against oxidative stress in diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus. There is much evidence showing that a high level of mitochondrial overproduction of reactive oxygen species in the diabetic retina contributes in modifying cellular signalling and leads to retinal cell damage and finally to the development of DR pathogenesis. In the last few decades, it has been reported that vitamin D is involved in DR pathogenesis. Vitamin D, traditionally known as an essential nutrient crucial in bone metabolism, has also been proven to be a very effective antioxidant. It has been demonstrated that it modulates the production of advanced glycosylated end products, as well as several pathways including protein kinase C, the polyol pathway leading to the reduction of free radical formation. It prevents the translocation of nuclear factor kappa B, preventing the inflammatory response, acting as an immunomodulator, and modulates autophagy and apoptosis. In this review, we explore the molecular mechanisms by which vitamin D protects the eye from oxidative stress, in order to evaluate whether vitamin D supplementation may be useful to mitigate the deleterious effects of free radicals in DR.

Therapeutic Approach of Flavonoid in Ameliorating Diabetic Cardiomyopathy by Targeting Mitochondrial-Induced Oxidative Stress

Diabetes cardiomyopathy is one of the key factors of mortality among diabetic patients around the globe. One of the prior contributors to the progression of diabetic cardiomyopathy is cardiac mitochondrial dysfunction. The cardiac mitochondrial dysfunction can induce oxidative stress in cardiomyocytes and was found to be the cause of majority of the heart morphological and dynamical changes in diabetic cardiomyopathy. To slow down the occurrence of diabetic cardiomyopathy, it is crucial to discover therapeutic agents that target mitochondrial-induced oxidative stress. Flavonoid is a plentiful phytochemical in plants that shows a wide range of biological actions against human diseases. Flavonoids have been extensively documented for their ability to protect the heart from diabetic cardiomyopathy. Flavonoids' ability to alleviate diabetic cardiomyopathy is primarily attributed to their antioxidant properties. In this review, we present the mechanisms involved in flavonoid therapies in ameliorating mitochondrial-induced oxidative stress in diabetic cardiomyopathy.

Glycation and Glycosylation in Cardiovascular Remodeling: Focus on Advanced Glycation End Products and O-Linked Glycosylations as Glucose-Related Pathogenetic Factors and Disease Markers

Glycation and glycosylation are non-enzymatic and enzymatic reactions, respectively, of glucose, glucose metabolites, and other reducing sugars with different substrates, such as proteins, lipids, and nucleic acids. Increased availability of glucose is a recognized risk factor for the onset and progression of diabetes-mellitus-associated disorders, among which cardiovascular diseases have a great impact on patient mortality. Both advanced glycation end products, the result of non-enzymatic glycation of substrates, and O-linked-N-Acetylglucosaminylation, a glycosylation reaction that is controlled by O-N-AcetylGlucosamine (GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), have been shown to play a role in cardiovascular remodeling. In this review, we aim (1) to summarize the most recent data regarding the role of glycation and O-linked-N-Acetylglucosaminylation as glucose-related pathogenetic factors and disease markers in cardiovascular remodeling, and (2) to discuss potential common mechanisms linking these pathways to the dysregulation and/or loss of function of different biomolecules involved in this field.

Metformin in cardiovascular diabetology: a focused review of its impact on endothelial function

As a first-line treatment for diabetes, the insulin-sensitizing biguanide, metformin, regulates glucose levels and positively affects cardiovascular function in patients with diabetes and cardiovascular complications. Endothelial dysfunction (ED) represents the primary pathological change of multiple vascular diseases, because it causes decreased arterial plasticity, increased vascular resistance, reduced tissue perfusion and atherosclerosis. Caused by “biochemical injury”, ED is also an independent predictor of cardiovascular events. Accumulating evidence shows that metformin improves ED through liver kinase B1 (LKB1)/5'-adenosine monophosphat-activated protein kinase (AMPK) and AMPK-independent targets, including nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt), endothelial nitric oxide synthase (eNOS), sirtuin 1 (SIRT1), forkhead box O1 (FOXO1), krüppel-like factor 4 (KLF4) and krüppel-like factor 2 (KLF2). Evaluating the effects of metformin on endothelial cell functions would facilitate our understanding of the therapeutic potential of metformin in cardiovascular diabetology (including diabetes and its cardiovascular complications). This article reviews the physiological and pathological functions of endothelial cells and the intact endothelium, reviews the latest research of metformin in the treatment of diabetes and related cardiovascular complications, and focuses on the mechanism of action of metformin in regulating endothelial cell functions.

SIRT1 Activation by Polydatin Alleviates Oxidative Damage and Elevates Mitochondrial Biogenesis in Experimental Diabetic Neuropathy

Mitochondrial dysfunction has been implicated as a one of the major factors linked to the development of painful diabetic neuropathy (DN). Several studies have demonstrated that sirtuin (SIRT1) activation recuperates nerve function by activating mitochondrial biogenesis. Polydatin, a resveratrol glycoside, has been explored to improve mitochondrial function via SIRT1 activation. However, the neuroprotective effects of polydatin in DN remain elusive. In this study, polydatin (25 and 50 mg/kg, oral) was administered for last 2 weeks of 8-week study to diabetic Sprague-Dawley rats weighing 250-300 g (post 6-weeks of streptozotocin 55 mg/kg, intraperitoneal). Treatment with polydatin significantly attenuated mechanical and thermal hyperalgesia in diabetic rats. Treated diabetic rats also showed improvement in motor/sensory nerve conduction velocities and nerve blood flow. For in vitro studies, Neuro2a cells were exposed to high-glucose (30 mM) condition to simulate short-term hyperglycemia. Polydatin was evaluated for its role in SIRT1 and Nrf2 activation at a dose of 5, 10, and 20 µM concentrations. Polydatin exposure normalized the mitochondrial superoxides, membrane potentials and improved neurite outgrowth in high-glucose-exposed Neuro2a cells. Increased SIRT1 activation by polydatin resulted in peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis. SIRT1 activation also facilitated Nrf2-directed antioxidant signaling. Study results inferred that decline in mitochondrial biogenesis and oxidative function in diabetic rats and high-glucose-exposed Neuro2a cells, could be counteracted by polydatin administration, postulated via enhancing SIRT1 and Nrf2 axis.

A Comprehensive Review of Neuronal Changes in Diabetics

There has been an exponential rise in diabetes mellitus (DM) cases on a global scale. Diabetes affects almost every system of the body, and the nervous system is no exception. Although the brain is dependent on glucose, providing it with the energy required for optimal functionality, glucose also plays a key role in the regulation of oxidative stress, cell death, among others, which furthermore contribute to the pathophysiology of neurological disorders. The variety of biochemical processes engaged in this process is only matched by the multitude of clinical consequences resulting from it. The wide-ranging effects on the central and peripheral nervous system include, but are not limited to axonopathies, neurodegenerative diseases, neurovascular diseases, and general cognitive impairment. All language search was conducted on MEDLINE, COCHRANE, EMBASE, and GOOGLE SCHOLAR till September 2021. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "CNS," "Diabetic Neuropathy," and "Insulin." We explored the literature on diabetic neuropathy, covering its epidemiology, pathophysiology with the respective molecular pathways, clinical consequences with a special focus on the central nervous system and finally, measures to prevent and treat neuronal changes. Diabetes is slowly becoming an epidemic, rapidly increasing the clinical burden on account of its wide-ranging complications. This review focuses on the neuronal changes occurring in diabetes such as the impact of hyperglycemia on brain function and structure, its association with various neurological disorders, and a few diabetes-induced peripheral neuropathic changes. It is an attempt to summarize the relevant literature about neuronal consequences of DM as treatment options available today are mostly focused on achieving better glycemic control; further research on novel treatment options to prevent or delay the progression of neuronal changes is still needed.