The missing link: a single unifying mechanism for diabetic complications

Mitochondrial DNA transcription and mitochondrial genome-encoded long noncoding RNA in diabetic retinopathy

In diabetic retinopathy, mitochondrial DNA (mtDNA) is damaged and mtDNA-encoded genes and long noncoding RNA cytochrome B (LncCytB) are downregulated. LncRNAs lack an open reading frame, but they can regulate gene expression by associating with DNA/RNA/protein. Double stranded mtDNA has promoters on both heavy (HSP) and light (LSP) strands with binding sites for mitochondrial transcription factor A (TFAM) between them. The aim was to investigate the role of LncCytB in mtDNA transcription in diabetic retinopathy. Using human retinal endothelial cells incubated in high glucose, the effect of regulation of LncCytB on TFAM binding at mtDNA promoters was investigated by Chromatin immunoprecipitation, and binding of LncCytB at TFAM by RNA immunoprecipitation and RNA fluorescence in situ hybridization. High glucose decreased TFAM binding at both HSP and LSP, and binding of LncCytB at TFAM. While LncCytB overexpression ameliorated decrease in TFAM binding and transcription of genes encoded by both H- and L- strands, LncCytB-siRNA further downregulated them. Maintenance of mitochondrial homeostasis by overexpressing mitochondrial superoxide dismutase or Sirtuin-1 protected diabetes-induced decrease in TFAM binding at mtDNA and LncCytB binding at TFAM, and mtDNA transcription. Similar results were obtained from mouse retinal microvessels from streptozotocin-induced diabetic mice. Thus, LncCytB facilitates recruitment of TFAM at HSP and LSP, and its downregulation in diabetes compromises the binding, resulting in the downregulation of polypeptides encoded by mtDNA. Regulation of LncCytB, in addition to protecting mitochondrial genomic stability, should also help in maintaining the transcription of mtDNA encoded genes and electron transport chain integrity in diabetic retinopathy.

Design and Development of a Non-invasive Opto-Electronic Sensor for Blood Glucose Monitoring Using a Visible Light Source

Background The management of diabetes is critically dependent on the continuous monitoring of blood glucose levels. Contemporary approaches primarily utilize invasive methods, which often prove to be uncomfortable and can deter patient adherence. There is a pressing need for the development of novel strategies that improve patient compliance and simplify the process of glucose monitoring. Aim and objectives The primary objective of this research is to develop a non-invasive blood glucose monitoring system (NIBGMS) that offers a convenient alternative to conventional invasive methods. This study aims to demonstrate the feasibility and accuracy of using visible laser light at a wavelength of 650 nm for glucose monitoring and to address physiological and technical challenges associated with in vivo measurements. Methods Our approach involved the design of a device that exploits the quantitative relationship between glucose concentration and the refraction phenomena of laser light. The system was initially calibrated and tested using glucose solutions across a range of concentrations (25-500 mg/dL). To get around the problems that come up when people's skin and bodies are different, we combined an infrared (IR) transmitter (800 nm) and receiver that checks for changes in voltage, which are indicative of glucose levels. Results The prototype device was compared with a commercially available blood glucose monitor (Accu-Chek active machine; Roche Diabetes Care, Inc., Mumbai, India). The results demonstrated an average linearity of 95.7% relative to the Accu-Chek machine, indicating a high level of accuracy in the non-invasive measurement of glucose levels. Conclusions The findings suggest that our NIBGMS holds significant promise for clinical application. It reduces the discomfort associated with blood sampling and provides reliable measurements that are comparable to those of existing invasive methods. The successful development of this device paves the way for further commercial translation and could significantly improve the quality of life for individuals with diabetes, by facilitating easier and more frequent monitoring.

Correlation Between Serum Vitamin E and HOMA-IR in Patients with T2DM

Background

Peroxidation is one of the important causes of insulin resistance (IR), and vitamin E is a natural antioxidant, and there may be some correlation between serum vitamin E levels and insulin resistance.

Purpose

The correlation between serum vitamin E and insulin resistance in type 2 diabetes mellitus (T2DM) population.

Methods

Two hundred and forty-two people (119 with T2DM) were included. One hundred and nineteen patients with T2DM were selected as the case group, and 123 people with non-T2DM were selected as the control group. People insulin resistance was detected by the homeostasis model assessment method (HOMA-IR) greater than 2.69 were included in the diabetic insulin resistance group, and those with HOMA-IR less than 2.69 were included in the diabetic non-insulin resistance group. Record the general body indicators, biochemical indicators, hepatic function indicators, vitamin E, and other indicators. Correlation analysis, logistic regression, trend analysis, and restricted cubic spline (RCS) were performed using SPSS 25.0 and R 4.1.1 software. Correlation analysis, logistic regression, trend analysis, restricted cubic spline (RCS) analysis were conducted on general body indicators, biochemical indicators, hepatic function indicators, vitamin E, and other indicators.

Results

The logistic regression results showed that after adjusting for confounding factors, vitamin E was an independent influencing factor for insulin resistance in T2DM patients (P < 0.001). The trend analysis results show that with the decrease of serum vitamin E levels, the risk of insulin resistance in T2DM patients gradually increases. The RCS results showed that the risk of insulin resistance was significantly increased when the serum vitamin E level was lower than 10,575.23 ng/mL.

Conclusion

Serum vitamin E levels are lower in T2DM patients than in healthy populations; Vitamin E is an independent influencing factor for HOMA-IR in T2DM patients. The risk of insulin resistance gradually increases in T2DM patients as serum vitamin E levels decrease. Vitamin E is a risk factor for insulin resistance at serum vitamin E levels below 10,575.23 ng/mL. At higher serum vitamin E levels than 10,575.23 ng/mL, vitamin E is a protective factor for insulin resistance.

NDUFS4 regulates cristae remodeling in diabetic kidney disease

The mitochondrial electron transport chain (ETC) is a highly adaptive process to meet metabolic demands of the cell, and its dysregulation has been associated with diverse clinical pathologies. However, the role and nature of impaired ETC in kidney diseases remains poorly understood. Here, we generate diabetic mice with podocyte-specific overexpression of Ndufs4, an accessory subunit of mitochondrial complex I, as a model investigate the role of ETC integrity in diabetic kidney disease (DKD). We find that conditional male mice with genetic overexpression of Ndufs4 exhibit significant improvements in cristae morphology, mitochondrial dynamics, and albuminuria. By coupling proximity labeling with super-resolution imaging, we also identify the role of cristae shaping protein STOML2 in linking NDUFS4 with improved cristae morphology. Together, we provide the evidence on the central role of NDUFS4 as a regulator of cristae remodeling and mitochondrial function in kidney podocytes. We propose that targeting NDUFS4 represents a promising approach to slow the progression of DKD.

The Protective Effects of Vitamin B Complex on Diclofenac Sodium-Induced Nephrotoxicity: The Role of NOX4/RhoA/ROCK

Diclofenac sodium (DIC) is a widely used non-steroidal anti-inflammatory drug. Unfortunately, its prolonged use is associated with nephrotoxicity due to oxidative stress, inflammation, and fibrosis. We aimed to investigate the nephroprotective effects of vitamin B complex (B1, B6, B12) against DIC-induced nephrotoxicity and its impact on NOX4/RhoA/ROCK, a pathway that plays a vital role in renal pathophysiology. Thirty-two Wistar rats were divided into four groups: (1) normal control; (2) vitamin B complex (16 mg/kg B1, 16 mg/kg B6, 0.16 mg/kg B12, intraperitoneal); (3) DIC (10 mg/kg, intramuscular); and (4) DIC plus vitamin B complex group. After 14 days, the following were assayed: serum renal biomarkers (creatinine, blood urea nitrogen, kidney injury molecule-1), oxidative stress, inflammatory (tumor necrosis factor-α, interleukin-6), and fibrotic (transforming growth factor-β) markers as well as the protein levels of NOX4, RhoA, and ROCK. Structural changes, inflammatory cell infiltration, and fibrosis were detected using hematoxylin and eosin and Masson trichrome stains. Compared to DIC, vitamin B complex significantly decreased the renal function biomarkers, markers of oxidative stress and inflammation, and fibrotic cytokines. Glomerular and tubular damage, inflammatory infiltration, and excessive collagen accumulation were also reduced. Protein levels of NOX4, RhoA, and ROCK were significantly elevated by DIC, and this elevation was ameliorated by vitamin B complex. In conclusion, vitamin B complex administration could be a renoprotective approach during treatment with DIC via, at least in part, suppressing the NOX4/RhoA/ROCK pathway.

MicroRNA 9 Is a Regulator of Endothelial to Mesenchymal Transition in Diabetic Retinopathy

Purpose

Diabetic retinopathy (DR) is a significant cause of blindness. Most research around DR focus on late-stage developments rather than early changes such as early endothelial dysfunction. Endothelial-to-mesenchymal transition (EndMT), an epigenetically regulated process whereby endothelial cells lose endothelial characteristics and adopt mesenchymal-like phenotypes, contributes to early endothelial changes in DR. The epigenetic regulator microRNA 9 (miR-9) is suppressed in the eyes during DR. MiR-9 plays a role in various diseases and regulates EndMT-related processes in other organs. We investigated the role miR-9 plays in glucose-induced EndMT in DR.

Methods

We examined the effects of glucose on miR-9 and EndMT using human retinal endothelial cells (HRECs). We then used HRECs and an endothelial-specific miR-9 transgenic mouse line to investigate the effect of miR-9 on glucose-induced EndMT. Finally, we used HRECs to probe the mechanisms through which miR-9 may regulate EndMT.

Results

We found that miR-9 inhibition was both necessary and sufficient for glucose-induced EndMT. Overexpression of miR-9 prevented glucose-induced EndMT, whereas suppressing miR-9 caused glucose-like EndMT changes. We also found that preventing EndMT with miR-9 overexpression improved retinal vascular leakage in DR. Finally, we showed that miR-9 regulates EndMT at an early stage by regulating EndMT-inducing signals such as proinflammatory and TGF-β pathways.

Conclusions

We have shown that miR-9 is an important regulator of EndMT in DR, potentially making it a good target for RNA-based therapy in early DR.

The "sweet" path to cancer: focus on cellular glucose metabolism

The hypoxia-inducible factor-1α (HIF-1α), a key player in the adaptive regulation of energy metabolism, and the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2), a critical regulator of glucose consumption, are the main drivers of the metabolic rewiring in cancer cells. The use of glycolysis rather than oxidative phosphorylation, even in the presence of oxygen (i.e., Warburg effect or aerobic glycolysis), is a major metabolic hallmark of cancer. Aerobic glycolysis is also important for the immune system, which is involved in both metabolic disorders development and tumorigenesis. More recently, metabolic changes resembling the Warburg effect have been described in diabetes mellitus (DM). Scientists from different disciplines are looking for ways to interfere with these cellular metabolic rearrangements and reverse the pathological processes underlying their disease of interest. As cancer is overtaking cardiovascular disease as the leading cause of excess death in DM, and biological links between DM and cancer are incompletely understood, cellular glucose metabolism may be a promising field to explore in search of connections between cardiometabolic and cancer diseases. In this mini-review, we present the state-of-the-art on the role of the Warburg effect, HIF-1α, and PKM2 in cancer, inflammation, and DM to encourage multidisciplinary research to advance fundamental understanding in biology and pathways implicated in the link between DM and cancer.

SGLT2 Inhibitor—Dapagliflozin Attenuates Diabetes-Induced Renal Injury by Regulating Inflammation through a CYP4A/20-HETE Signaling Mechanism

Diabetic kidney disease (DKD) is a serious complication of diabetes, affecting millions of people worldwide. Inflammation and oxidative stress are key contributors to the development and progression of DKD, making them potential targets for therapeutic interventions. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have emerged as a promising class of drugs, with evidence demonstrating that they can improve renal outcomes in people with diabetes. However, the exact mechanism by which SGLT2i exert their renoprotective effects is not yet fully understood. This study demonstrates that dapagliflozin treatment attenuates renal injury observed in type 2 diabetic mice. This is evidenced by the reduction in renal hypertrophy and proteinuria. Furthermore, dapagliflozin decreases tubulointerstitial fibrosis and glomerulosclerosis by mitigating the generation of reactive oxygen species and inflammation, which are activated through the production of CYP4A-induced 20-HETE. Our findings provide insights onto a novel mechanistic pathway by which SGLT2i exerts their renoprotective effects. Overall, and to our knowledge, the study provides critical insights into the pathophysiology of DKD and represents an important step towards improving outcomes for people with this devastating condition.

Anesthetic Considerations in Dogs and Cats with Diabetes Mellitus

Understanding the effects of diabetes and hyperglycemia on hydration, acid-base status, and immune function is paramount to safely anesthetizing diabetic cats and dogs. Preoperative stabilization of glucose concentrations, hydration, and electrolyte imbalances is key to minimizing morbidity and mortality. Blood glucose monitoring perioperatively will help guide insulin and dextrose administration. Specific anesthetic considerations, and peri-anesthetic management of animals with diabetes mellitus, including anesthetic drugs and recommended insulin protocols are discussed.

Natural Monoterpenes as Potential Therapeutic Agents against Atherosclerosis

Traditional herbal medicines based on natural products play a pivotal role in preventing and managing atherosclerotic diseases, which are among the leading causes of death globally. Monoterpenes are a large class of naturally occurring compounds commonly found in many aromatic and medicinal plants. Emerging evidence has shown that monoterpenes have many biological properties, including cardioprotective effects. Remarkably, an increasing number of studies have demonstrated the therapeutic potential of natural monoterpenes to protect against the pathogenesis of atherosclerosis. These findings shed light on developing novel effective antiatherogenic drugs from these compounds. Herein, we provide an overview of natural monoterpenes' effects on atherogenesis and the underlying mechanisms. Monoterpenes have pleiotropic and multitargeted pharmacological properties by interacting with various cell types and intracellular molecular pathways involved in atherogenesis. These properties confer remarkable advantages in managing atherosclerosis, which has been recognized as a multifaceted vascular disease. We also discuss limitations in the potential clinical application of monoterpenes as therapeutic agents against atherosclerosis. We propose perspectives to give new insights into future preclinical research and clinical practice regarding natural monoterpenes.

Differences in junction-associated gene expression changes in three rat models of diabetic retinopathy with similar neurovascular phenotype

Diabetic retinopathy, also defined as microvascular complication of diabetes mellitus, affects the entire neurovascular unit with specific aberrations in every compartment. Neurodegeneration, glial activation and vasoregression are observed consistently in models of diabetic retinopathy. However, the order and the severity of these aberrations varies in different models, which is also true in patients. In this study, we analysed rat models of diabetic retinopathy with similar phenotypes to identify key differences in the pathogenesis. For this, we focussed on intercellular junction-associated gene expression, which are important for the communication and homeostasis within the neurovascular unit. Streptozotocin-injected diabetic Wistar rats, methylglyoxal supplemented Wistar rats and polycystin-2 transgenic (PKD) rats were analysed for neuroretinal function, vasoregression and retinal expression of junction-associated proteins. In all three models, neuroretinal impairment and vasoregression were observed, but gene expression profiling of junction-associated proteins demonstrated nearly no overlap between the three models. However, the differently expressed genes were from the main classes of claudins, connexins and integrins in all models. Changes in Rcor1 expression in diabetic rats and Egr1 expression in PKD rats confirmed the differences in upstream transcription factor level between the models. In PKD rats, a possible role for miRNA regulation was observed, indicated by an upregulation of miR-26b-5p, miR-122-5p and miR-300-3p, which was not observed in the other models. In silico allocation of connexins revealed not only differences in regulated subtypes, but also in affected retinal cell types, as well as connexin specific upstream regulators Sox7 and miR-92a-3p. In this study, we demonstrate that, despite their similar phenotype, models for diabetic retinopathy exhibit significant differences in their pathogenic pathways and primarily affected cell types. These results underline the importance for more sensitive diagnostic tools to identify pathogenic clusters in patients as the next step towards a desperately needed personalized therapy.

CADD Studies in the Discovery of Potential ARI (Aldose Reductase Inhibitors) Agents for the Treatment of Diabetic Complications

The lack of currently available drugs for treating diabetes complications has stimulated our interest in finding new Aldose Reductase inhibitors (ARIs) with more beneficial biological properties. One metabolic method uses aldose reductase inhibitors in the first step of the polyol pathway to control excess glucose flux in diabetic tissues. Computer-aided drug discovery (CADD) is key in finding and optimizing potential lead substances. AR inhibitors (ARI) have been widely discussed in the literature. For example, Epalrestat is currently the only ARI used to treat patients with diabetic neuropathy in Japan, India, and China. Inhibiting R in patients with severe to moderate diabetic autonomic neuropathy benefits heart rate variability. AT-001, an AR inhibitor, is now being tested in COVID-19 to see how safe and effective it reduces inflammation and cardiac damage. In summary, these results from animal and human studies strongly indicate that AR can cause cardiovascular complications in diabetes. The current multi-center, large-scale randomized human study of the newly developed powerful ARI may prove its role in diabetic cardiovascular disease to establish therapeutic potential. During the recent coronavirus disease (COVID-19) outbreak in 2019, diabetes and cardiovascular disease were risk factors for severely negative clinical outcomes in patients with COVID19. New data shows that diabetes and obesity are among the strongest predictors of COVID-19 hospitalization. Patients and risk factors for severe morbidity and mortality of COVID- 19.

Hyperbaric oxygen therapy and chemokine administration - a combination with potential therapeutic value for treating diabetic wounds

Non-healing wounds impart serious medical problems to people with diabetes. Amongst 15% of diabetic patients, the incidence of foot ulcer is the most prevailing, which confers a significant risk of limb amputation, mainly due to hypoxia and impairment in cell signaling. Alteration in the expression of chemokines and the related factors in diabetic conditions delays the recruitment of different cell types, including fibroblasts, keratinocytes, and immune cells such as macrophages to the site of injury, further impairing neovasculogenesis, re-epithelialization, and extracellular matrix formation. Thus, proper activation of effector cells through an accurate signal pathway is necessary for better therapeutic application. Hyperbaric oxygen therapy (HBOT) is the current treatment prescribed by medical practitioners, shown to have increased the wound healing rate by reducing the need for significant amputation among the diabetic population. However, the risk of morbidity associated with HBOT needs complete attention through rigorous research to avoid adverse outcomes. Altering the level of pro-angiogenic chemokines may regulate the inflammatory response, further promote vascularization, and enhance the complete healing of wounds in diabetic patients. Thus, a combination of better therapeutic approaches could pave the way for developing a successful treatment for diabetic foot and wound healing.

Mutual Regulation between Redox and Hypoxia-Inducible Factors in Cardiovascular and Renal Complications of Diabetes

Oxidative stress and hypoxia-inducible factors (HIFs) have been implicated in the pathogenesis of diabetic cardiovascular and renal diseases. Reactive oxygen species (ROS) mediate physiological and pathophysiological processes, being involved in the modulation of cell signaling, differentiation, and survival, but also in cyto- and genotoxic damage. As master regulators of glycolytic metabolism and oxygen homeostasis, HIFs have been largely studied for their role in cell survival in hypoxic conditions. However, in addition to hypoxia, other stimuli can regulate HIFs stability and transcriptional activity, even in normoxic conditions. Among these, a regulatory role of ROS and their byproducts on HIFs, particularly the HIF-1α isoform, has received growing attention in recent years. On the other hand, HIF-1α and HIF-2α exert mutually antagonistic effects on oxidative damage. In diabetes, redox-mediated HIF-1α deregulation contributes to the onset and progression of cardiovascular and renal complications, and recent findings suggest that deranged HIF signaling induced by hyperglycemia and other cellular stressors associated with metabolic disorders may cause mitochondrial dysfunction, oxidative stress, and inflammation. Understanding the mechanisms of mutual regulation between HIFs and redox factors and the specific contribution of the two main isoforms of HIF-α is fundamental to identify new therapeutic targets for vascular complications of diabetes.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Selective protein kinase C inhibition switches time-dependent glucose cardiotoxicity to cardioprotection

Hyperglycaemia at the time of myocardial infarction has an adverse effect on prognosis irrespective of a prior diagnosis of diabetes, suggesting glucose is the damaging factor. In ex vivo models of ischaemia, we demonstrated that deleterious effects of acutely elevated glucose are PKCα/β-dependent, and providing PKCα/β are inhibited, elevated glucose confers cardioprotection. Short pre-treatments with high glucose were used to investigate time-dependent glucose cardiotoxicity, with PKCα/β inhibition investigated as a potential mechanism to reverse the toxicity. Freshly isolated non-diabetic rat cardiomyocytes were exposed to elevated glucose to investigate the time-dependence toxic effects. High glucose challenge for >7.5 min was cardiotoxic, proarrhythmic and lead to contractile failure, whilst cardiomyocytes exposed to metabolic inhibition following 5-min high glucose, displayed a time-dependent protection lasting ∼15 min. This protection was further enhanced with PKCα/β inhibition. Cardioprotection was measured as a delay in contractile failure and K_ATP channel activation, improved contractile and Ca²⁺ transient recovery and increased cell survival. Finally, the effects of pre-ischaemic treatment with high glucose in a whole-heart coronary ligation protocol, where protection was evident with PKCα/β inhibition. Selective PKCα/β inhibition enhances protection suggesting glycaemic control with PKC inhibition as a potential cardioprotective therapeutics in myocardial infarction and elective cardiac surgery.

Oxidative Stress and Mitochondrial Dysfunction Associated with Peripheral Neuropathy in Type 1 Diabetes

Significance: This review highlights the many intracellular processes generating reactive oxygen species (ROS) in the peripheral nervous system in the context of type 1 diabetes. The major sources of superoxide and hydrogen peroxide (H₂O₂) are described, and scavenging systems are explained. Important roles of ROS in regulating normal redox signaling and in a disease setting, such as diabetes, contributing to oxidative stress and cellular damage are outlined. The primary focus is the role of hyperglycemia in driving elevated ROS production and oxidative stress contributing to neurodegeneration in diabetic neuropathy (within the dorsal root ganglia [DRG] and peripheral nerve). Recent Advances: Contributors to ROS production under high intracellular glucose concentration such as mitochondria and the polyol pathway are discussed. The primarily damaging impact of ROS on multiple pathways including mitochondrial function, endoplasmic reticulum (ER) stress, autophagy, and epigenetic signaling is covered. Critical Issues: There is a strong focus on mechanisms of diabetes-induced mitochondrial dysfunction and how this may drive ROS production (in particular superoxide). The mitochondrial sites of superoxide/H₂O₂ production via mitochondrial metabolism and aerobic respiration are reviewed. Future Directions: Areas for future development are highlighted, including the need to clarify diabetes-induced changes in autophagy and ER function in neurons and Schwann cells. In addition, more clarity is needed regarding the sources of ROS production at mitochondrial sites under high glucose concentration (and lack of insulin signaling). New areas of study should be introduced to investigate the role of ROS, nuclear lamina function, and epigenetic signaling under diabetic conditions in peripheral nerve.

The mechanisms of glycolipid metabolism disorder on vascular injury in type 2 diabetes

Patients with diabetes have severe vascular complications, such as diabetic nephropathy, diabetic retinopathy, cardiovascular disease, and neuropathy. Devastating vascular complications lead to increased mortality, blindness, kidney failure, and decreased overall quality of life in people with type 2 diabetes (T2D). Glycolipid metabolism disorder plays a vital role in the vascular complications of T2D. However, the specific mechanism of action remains to be elucidated. In T2D patients, vascular damage begins to develop before insulin resistance and clinical diagnosis. Endothelial dysregulation is a significant cause of vascular complications and the early event of vascular injury. Hyperglycemia and hyperlipidemia can trigger inflammation and oxidative stress, which impair endothelial function. Furthermore, during the pathogenesis of T2D, epigenetic modifications are aberrant and activate various biological processes, resulting in endothelial dysregulation. In the present review, we provide an overview and discussion of the roles of hyperglycemia- and hyperlipidemia-induced endothelial dysfunction, inflammatory response, oxidative stress, and epigenetic modification in the pathogenesis of T2D. Understanding the connections of glucotoxicity and lipotoxicity with vascular injury may reveal a novel potential therapeutic target for diabetic vascular complications.

Mitochondrial Dysfunction and Cardiovascular Disease: Pathophysiology and Emerging Therapies

Mitochondria ensure the supply of cellular energy through the production of ATP via oxidative phosphorylation. The alteration of this process, called mitochondrial dysfunction, leads to a reduction in ATP and an increase in the production of reactive oxygen species (ROS). Mitochondrial dysfunction can be caused by mitochondrial/nuclear DNA mutations, or it can be secondary to pathological conditions such as cardiovascular disease, aging, and environmental stress. The use of therapies aimed at the prevention/correction of mitochondrial dysfunction, in the context of the specific treatment of cardiovascular diseases, is a topic of growing interest. In this context, the data are conflicting since preclinical studies are numerous, but there are no large randomized studies.

Empagliflozin mitigates type 2 diabetes-associated peripheral neuropathy: a glucose-independent effect through AMPK signaling

Diabetic peripheral neuropathy (DPN) represents a severe microvascular condition that dramatically affects diabetic patients despite adequate glycemic control, resulting in high morbidity. Thus, recently, anti-diabetic drugs that possess glucose-independent mechanisms attracted attention. This work aims to explore the potentiality of the selective sodium-glucose cotransporter-2 inhibitor, empagliflozin (EMPA), to ameliorate streptozotocin-induced DPN in rats with insight into its precise signaling mechanism. Rats were allocated into four groups, where control animals received vehicle daily for 2 weeks. In the remaining groups, DPN was elicited by single intraperitoneal injections of freshly prepared streptozotocin and nicotinamide (52.5 and 50 mg/kg, respectively). Then EMPA (3 mg/kg/p.o.) was given to two groups either alone or accompanied with the AMPK inhibitor dorsomorphin (0.2 mg/kg/i.p.). Despite the non-significant anti-hyperglycemic effect, EMPA improved sciatic nerve histopathological alterations, scoring, myelination, nerve fibers’ count, and nerve conduction velocity. Moreover, EMPA alleviated responses to different nociceptive stimuli along with improved motor coordination. EMPA modulated ATP/AMP ratio, upregulated p-AMPK while reducing p-p38 MAPK expression, p-ERK1/2 and consequently p-NF-κB p65 as well as its downstream mediators (TNF-α and IL-1β), besides enhancing SOD activity and lowering MDA content. Moreover, EMPA downregulated mTOR and stimulated ULK1 as well as beclin-1. Likewise, EMPA reduced miR-21 that enhanced RECK, reducing MMP-2 and -9 contents. EMPA’s beneficial effects were almost abolished by dorsomorphin administration. In conclusion, EMPA displayed a protective effect against DPN independently from its anti-hyperglycemic effect, probably via modulating the AMPK pathway to modulate oxidative and inflammatory burden, extracellular matrix remodeling, and autophagy.

Empagliflozin mitigates type 2 diabetes-associated peripheral neuropathy: a glucose-independent effect through AMPK signaling

Diabetic peripheral neuropathy (DPN) represents a severe microvascular condition that dramatically affects diabetic patients despite adequate glycemic control, resulting in high morbidity. Thus, recently, anti-diabetic drugs that possess glucose-independent mechanisms attracted attention. This work aims to explore the potentiality of the selective sodium-glucose cotransporter-2 inhibitor, empagliflozin (EMPA), to ameliorate streptozotocin-induced DPN in rats with insight into its precise signaling mechanism. Rats were allocated into four groups, where control animals received vehicle daily for 2 weeks. In the remaining groups, DPN was elicited by single intraperitoneal injections of freshly prepared streptozotocin and nicotinamide (52.5 and 50 mg/kg, respectively). Then EMPA (3 mg/kg/p.o.) was given to two groups either alone or accompanied with the AMPK inhibitor dorsomorphin (0.2 mg/kg/i.p.). Despite the non-significant anti-hyperglycemic effect, EMPA improved sciatic nerve histopathological alterations, scoring, myelination, nerve fibers' count, and nerve conduction velocity. Moreover, EMPA alleviated responses to different nociceptive stimuli along with improved motor coordination. EMPA modulated ATP/AMP ratio, upregulated p-AMPK while reducing p-p38 MAPK expression, p-ERK1/2 and consequently p-NF-κB p65 as well as its downstream mediators (TNF-α and IL-1β), besides enhancing SOD activity and lowering MDA content. Moreover, EMPA downregulated mTOR and stimulated ULK1 as well as beclin-1. Likewise, EMPA reduced miR-21 that enhanced RECK, reducing MMP-2 and -9 contents. EMPA's beneficial effects were almost abolished by dorsomorphin administration. In conclusion, EMPA displayed a protective effect against DPN independently from its anti-hyperglycemic effect, probably via modulating the AMPK pathway to modulate oxidative and inflammatory burden, extracellular matrix remodeling, and autophagy.

Modulation of Reactive Oxygen Species Homeostasis as a Pleiotropic Effect of Commonly Used Drugs

Age-associated diseases represent a growing burden for global health systems in our aging society. Consequently, we urgently need innovative strategies to counteract these pathological disturbances. Overwhelming generation of reactive oxygen species (ROS) is associated with age-related damage, leading to cellular dysfunction and, ultimately, diseases. However, low-dose ROS act as crucial signaling molecules and inducers of a vaccination-like response to boost antioxidant defense mechanisms, known as mitohormesis. Consequently, modulation of ROS homeostasis by nutrition, exercise, or pharmacological interventions is critical in aging. Numerous nutrients and approved drugs exhibit pleiotropic effects on ROS homeostasis. In the current review, we provide an overview of drugs affecting ROS generation and ROS detoxification and evaluate the potential of these effects to counteract the development and progression of age-related diseases. In case of inflammation-related dysfunctions, cardiovascular- and neurodegenerative diseases, it might be essential to strengthen antioxidant defense mechanisms in advance by low ROS level rises to boost the individual ROS defense mechanisms. In contrast, induction of overwhelming ROS production might be helpful to fight pathogens and kill cancer cells. While we outline the potential of ROS manipulation to counteract age-related dysfunction and diseases, we also raise the question about the proper intervention time and dosage.

Antioxidative Activity Evaluation of High Purity and Micronized Tartary Buckwheat Flavonoids Prepared by Antisolvent Recrystallization

Tartary buckwheat, a healthy food, is associated with a reduced risk of certain human chronic diseases. However, the bioactive component flavonoids in Tartary buckwheat have poor solubility and low absorption in vivo. To improve these points, 60.00% Tartary buckwheat total flavonoids (TFs) were obtained by ethanol refluxing method, which were purified and micronized by antisolvent recrystallization (ASR) using methanol as a solvent and deionized water as an antisolvent. By using High Performance Liquid Chromatography (HPLC) and electrospray ionized mass spectrometry (ESI-MS), the main flavonoid in pure flavonoids (PF) were rutin (RU), kaempferol-3-O-rutinoside (KA) and quercetin (QU); the content of TF is 99.81% after purification. It is more worthy of our attention that micronized flavonoids contribute more to antioxidant activity because of good solubility. These results provide a theoretical reference for the micronization of other flavonoids.

Epigenetic Modifications and Non-Coding RNA in Diabetes-Mellitus-Induced Coronary Artery Disease: Pathophysiological Link and New Therapeutic Frontiers

Diabetes mellitus (DM) is a glucose metabolism disorder characterized by chronic hyperglycemia resulting from a deficit of insulin production and/or action. DM affects more than 1 in 10 adults, and it is associated with an increased risk of cardiovascular morbidity and mortality. Cardiovascular disease (CVD) accounts for two thirds of the overall deaths in diabetic patients, with coronary artery disease (CAD) and ischemic cardiomyopathy as the main contributors. Hyperglycemic damage on vascular endothelial cells leading to endothelial dysfunction represents the main initiating factor in the pathogenesis of diabetic vascular complications; however, the underlying pathophysiological mechanisms are still not entirely understood. This review addresses the current knowledge on the pathophysiological links between DM and CAD with a focus on the role of epigenetic modifications, including DNA methylation, histone modifications and noncoding RNA control. Increased knowledge of epigenetic mechanisms has contributed to the development of new pharmacological treatments (“epidrugs”) with epigenetic targets, although these approaches present several challenges. Specific epigenetic biomarkers may also be used to predict or detect the development and progression of diabetes complications. Further studies on diabetes and CAD epigenetics are needed in order to identify possible new therapeutic targets and advance personalized medicine with the prediction of individual drug responses and minimization of adverse effects.

Signaling Pathways Related to Oxidative Stress in Diabetic Cardiomyopathy

Diabetes is a chronic metabolic disease that is increasing in prevalence and causes many complications. Diabetic cardiomyopathy (DCM) is a complication of diabetes that is associated with high mortality, but it is not well defined. Nevertheless, it is generally accepted that DCM refers to a clinical disease that occurs in patients with diabetes and involves ventricular dysfunction, in the absence of other cardiovascular diseases, such as coronary atherosclerotic heart disease, hypertension, or valvular heart disease. However, it is currently uncertain whether the pathogenesis of DCM is directly attributable to metabolic dysfunction or secondary to diabetic microangiopathy. Oxidative stress (OS) is considered to be a key component of its pathogenesis. The production of reactive oxygen species (ROS) in cardiomyocytes is a vicious circle, resulting in further production of ROS, mitochondrial DNA damage, lipid peroxidation, and the post-translational modification of proteins, as well as inflammation, cardiac hypertrophy and fibrosis, ultimately leading to cell death and cardiac dysfunction. ROS have been shown to affect various signaling pathways involved in the development of DCM. For instance, OS causes metabolic disorders by affecting the regulation of PPARα, AMPK/mTOR, and SIRT3/FOXO3a. Furthermore, OS participates in inflammation mediated by the NF-κB pathway, NLRP3 inflammasome, and the TLR4 pathway. OS also promotes TGF-β-, Rho-ROCK-, and Notch-mediated cardiac remodeling, and is involved in the regulation of calcium homeostasis, which impairs ATP production and causes ROS overproduction. In this review, we summarize the signaling pathways that link OS to DCM, with the intention of identifying appropriate targets and new antioxidant therapies for DCM.

Long Noncoding RNAs and Mitochondrial Homeostasis in the Development of Diabetic Retinopathy

Retinopathy is one of the most devastating complications of diabetes, which a patient fears the most. Hyperglycemic environment results in many structural, functional, molecular and biochemical abnormalities in the retina, and overproduction of mitochondrial superoxide, induced by hyperglycemic milieu, is considered to play a central role in the development of diabetic retinopathy. Expression of many genes associated with maintaining mitochondrial homeostasis is also altered. Recent research has shown that several long noncoding RNAs, RNAs with more than 200 nucleotides but without any reading frames, are aberrantly expressed in diabetes, and altered expression of these long noncoding RNAs is now being implicated in the development of diabetes and its complications including retinopathy. This review focuses the role of long noncoding RNAs in the development of diabetic retinopathy, with a special emphasis on the maintenance of mitochondrial homeostasis.

Thiamine and diabetes: back to the future?

The first reports of a link between thiamine and diabetes date back to the 1940s. Some years later, a role for thiamine deficiency in diabetic neuropathy became evident, and some pilot studies evaluated the putative effects of thiamine supplementation. However, the administration of thiamine and its lipophilic derivative benfotiamine for the treatment of this complication gained consensus only at the end of the '90 s. The first evidence of the beneficial effects of thiamine on microvascular cells involved in diabetic complications dates to 1996: from then on, several papers based on in vitro and animal models have addressed the potential use of this vitamin in counteracting diabetic microangiopathy. A few pilot studies in humans reported beneficial effects of thiamine administration on diabetic nephropathy, but, despite all promising proofs-of-concept, the possible role of thiamine in counteracting development or progression of retinopathy has not been addressed until now. Thiamine is a water-soluble vitamin, rapidly expelled from the body, with no issues of over-dosage or accumulation; unfortunately, it is non-patentable, and neither industry nor independent donors are interested in investing in large-scale randomized controlled clinical trials to investigate its potential in diabetes and its complications. Consequently, science will not be able to disprove a promising hypothesis and, more importantly, diabetic people remain deprived of a possible way to ameliorate their condition.

Wogonin and alleviation of hyperglycemia via inhibition of DAG mediated PKC expression. A brief insight

Protein kinase C (PKC) is a family of protein kinase enzymes that can phosphorylate other proteins and influence their functions, such as signal transduction, cell survival, and death. Increased diacylglycerol (DAG) concentrations, which are typically observed raised in hyperglycemic situations such as diabetes mellitus, can also activate PKC enzymes (DM). On the other hand, PKC isomers have been shown to play an essential role in diabetes and many hyperglycemic complications, most importantly atherosclerosis and diabetic cardiomyopathy (DCM). As a result, blocking PKC activation via DAG can prevent hyperglycemia and related consequences, such as DCM. Wogonin is a herbal medicine which has anti-inflammatory properties, and investigations show that it scavenge oxidative radicals, attenuate nuclear factor-kappa B (NF-κB) activity, inhibit several essential cell cycle regulatory genes, block nitric oxide (NO) and suppress cyclooxygenase-2 (COX-2). Furthermore, several investigations show that wogonin also attenuates diacylglycerol DAG levels in diabetic mice. Since the DAG-PKC pathway is linked with hyperglycemia and its complications, Wogonin-mediated DAG-PKC attenuation can help treat hyperglycemia and its complications.

Mitochondrial Regulation of Diabetic Kidney Disease

The role and nature of mitochondrial dysfunction in diabetic kidney disease (DKD) has been extensively studied. Yet, the molecular drivers of mitochondrial remodeling in DKD are poorly understood. Diabetic kidney cells exhibit a cascade of mitochondrial dysfunction ranging from changes in mitochondrial morphology to significant alterations in mitochondrial biogenesis, biosynthetic, bioenergetics and production of reactive oxygen species (ROS). How these changes individually or in aggregate contribute to progression of DKD remain to be fully elucidated. Nevertheless, because of the remarkable progress in our basic understanding of the role of mitochondrial biology and its dysfunction in DKD, there is great excitement on future targeted therapies based on improving mitochondrial function in DKD. This review will highlight the latest advances in understanding the nature of mitochondria dysfunction and its role in progression of DKD, and the development of mitochondrial targets that could be potentially used to prevent its progression.

Development of Novel Indole-Based Bifunctional Aldose Reductase Inhibitors/Antioxidants as Promising Drugs for the Treatment of Diabetic Complications

Aldose reductase (AR, ALR2), the first enzyme of the polyol pathway, is implicated in the pathophysiology of diabetic complications. Aldose reductase inhibitors (ARIs) thus present a promising therapeutic approach to treat a wide array of diabetic complications. Moreover, a therapeutic potential of ARIs in the treatment of chronic inflammation-related pathologies and several genetic metabolic disorders has been recently indicated. Substituted indoles are an interesting group of compounds with a plethora of biological activities. This article reviews a series of indole-based bifunctional aldose reductase inhibitors/antioxidants (ARIs/AOs) developed during recent years. Experimental results obtained in in vitro, ex vivo, and in vivo models of diabetic complications are presented. Structure–activity relationships with respect to carboxymethyl pharmacophore regioisomerization and core scaffold modification are discussed along with the criteria of ‘drug-likeness”. Novel promising structures of putative multifunctional ARIs/AOs are designed.

Diabetic Complications and Oxidative Stress: A 20-Year Voyage Back in Time and Back to the Future

Twenty years have passed since Brownlee and colleagues proposed a single unifying mechanism for diabetic complications, introducing a turning point in this field of research. For the first time, reactive oxygen species (ROS) were identified as the causal link between hyperglycemia and four seemingly independent pathways that are involved in the pathogenesis of diabetes-associated vascular disease. Before and after this milestone in diabetes research, hundreds of articles describe a role for ROS, but the failure of clinical trials to demonstrate antioxidant benefits and some recent experimental studies showing that ROS are dispensable for the pathogenesis of diabetic complications call for time to reflect. This twenty-year journey focuses on the most relevant literature regarding the main sources of ROS generation in diabetes and their role in the pathogenesis of cell dysfunction and diabetic complications. To identify future research directions, this review discusses the evidence in favor and against oxidative stress as an initial event in the cellular biochemical abnormalities induced by hyperglycemia. It also explores possible alternative mechanisms, including carbonyl stress and the Warburg effect, linking glucose and lipid excess, mitochondrial dysfunction, and the activation of alternative pathways of glucose metabolism leading to vascular cell injury and inflammation.

Reduction of Glut1 in the Neural Retina But Not the RPE Alleviates Polyol Accumulation and Normalizes Early Characteristics of Diabetic Retinopathy

Hyperglycemia is a key determinant for development of diabetic retinopathy (DR). Inadequate glycemic control exacerbates retinopathy, while normalization of glucose levels delays its progression. In hyperglycemia, hexokinase is saturated and excess glucose is metabolized to sorbitol by aldose reductase via the polyol pathway. Therapies to reduce retinal polyol accumulation for the prevention of DR have been elusive because of low sorbitol dehydrogenase levels in the retina and inadequate inhibition of aldose reductase. Using systemic and conditional genetic inactivation, we targeted the primary facilitative glucose transporter in the retina, Glut1, as a preventative therapeutic in diabetic male and female mice. Unlike WT diabetics, diabetic Glut1 ^+/- mice did not display elevated Glut1 levels in the retina. Furthermore, diabetic Glut1 ^+/- mice exhibited ameliorated ERG defects, inflammation, and oxidative stress, which was correlated with a significant reduction in retinal sorbitol accumulation. Retinal pigment epithelium-specific reduction of Glut1 did not prevent an increase in retinal sorbitol content or early hallmarks of DR. However, like diabetic Glut1 ^+/- mice, reduction of Glut1 specifically in the retina mitigated polyol accumulation and diminished retinal dysfunction and the elevation of markers for oxidative stress and inflammation associated with diabetes. These results suggest that modulation of retinal polyol accumulation via Glut1 in photoreceptors can circumvent the difficulties in regulating systemic glucose metabolism and be exploited to prevent DR.SIGNIFICANCE STATEMENT Diabetic retinopathy affects one-third of diabetic patients and is the primary cause of vision loss in adults 20-74 years of age. While anti-VEGF and photocoagulation treatments for the late-stage vision threatening complications can prevent vision loss, a significant proportion of patients do not respond to anti-VEGF therapies, and mechanisms to stop progression of early-stage symptoms remain elusive. Glut1 is the primary facilitative glucose transporter for the retina. We determined that a moderate reduction in Glut1 levels, specifically in the retina, but not the retinal pigment epithelium, was sufficient to prevent retinal polyol accumulation and the earliest functional defects to be identified in the diabetic retina. Our study defines modulation of Glut1 in retinal neurons as a targetable molecule for prevention of diabetic retinopathy.

Taohuajing reduces oxidative stress and inflammation in diabetic cardiomyopathy through the sirtuin 1/nucleotide-binding oligomerization domain-like receptor protein 3 pathway

Background

Oxidative stress and inflammation promote the development of diabetic cardiomyopathy (DCM). Therefore, inhibiting these processes may show beneficial effects in the treatment of patients with DCM. Taohuajing (THJ) is prepared using Persicae semen (Taoren), Polygonatum sibiricum (Huangjing), and Carthami flos (Honghua) and may have applications in the treatment of DCM. However, the protective effects of THJ have not been thoroughly assessed. Accordingly, in this study, we aimed to investigate the protective effects of THJ in a model of DCM and further clarify the potential mechanisms.

Methods

A type 2 diabetes mellitus model was generated using male C57BL/6 mice. Echocardiography and histopathology were used to evaluate cardiac function. The expression levels of cytokines were measured using enzyme-linked immunosorbent assays. Western blotting and small interfering RNA were used to evaluate the targets of THJ.

Results

Compared with the control group, DCM mice showed cardiac dysfunction, metabolic disorder, fibrosis, and disorganized ultrastructure, and THJ treatment significantly inhibited these changes significantly. THJ treatment also inhibited the production of reactive oxygen species (ROS) and malondialdehyde (MDA), induced the production of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), decreased the levels of pro-inflammatory cytokines, and suppressed the activation of the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome. These protective effects were abolished by sirtinol, an inhibitor of sirtuin1 (SIRT1).

Conclusions

Overall, THJ protected the heart from hyperglycemia-induced oxidative stress and inflammation in DCM mice via a mechanism involving SIRT1-mediated antioxidant proteins and suppression of the NLRP3 inflammasome.

Structural insights into C1-ligand interactions: Filling the gaps by in silico methods

Protein Kinase C isoenzymes (PKCs) are the key mediators of the phosphoinositide signaling pathway, which involves regulated hydrolysis of phosphatidylinositol (4,5)-bisphosphate to diacylglycerol (DAG) and inositol-1,4,5-trisphosphate. Dysregulation of PKCs is implicated in many human diseases making this class of enzymes an important therapeutic target. Specifically, the DAG-sensing cysteine-rich conserved homology-1 (C1) domains of PKCs have emerged as promising targets for pharmaceutical modulation. Despite significant progress, the rational design of the C1 modulators remains challenging due to difficulties associated with structure determination of the C1-ligand complexes. Given the dearth of experimental structural data, computationally derived models have been instrumental in providing atomistic insight into the interactions of the C1 domains with PKC agonists. In this review, we provide an overview of the in silico approaches for seven classes of C1 modulators and outline promising future directions.

CYP450 Mediates Reactive Oxygen Species Production in a Mouse Model of β-Thalassemia through an Increase in 20-HETE Activity

Oxidative damage by reactive oxygen species (ROS) is one of the main contributors to cell injury and tissue damage in thalassemia patients. Recent studies suggest that ROS generation in non-transfusion-dependent (NTDT) patients occurs as a result of iron overload. Among the different sources of ROS, the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family of enzymes and cytochrome P450 (CYP450) have been proposed to be major contributors for oxidative stress in several diseases. However, the sources of ROS in patients with NTDT remain poorly understood. In this study, Hbbth3/+ mice, a mouse model for β-thalassemia, were used. These mice exhibit an unchanged or decreased expression of the major NOX isoforms, NOX1, NOX2 and NOX4, when compared to their C57BL/6 control littermates. However, a significant increase in the protein synthesis of CYP4A and CYP4F was observed in the Hbbth3/+ mice when compared to the C57BL/6 control mice. These changes were paralleled by an increased production of 20-hydroxyeicosatetraenoic acid (20-HETE), a CYP4A and CYP4F metabolite. Furthermore, these changes corroborate with onset of ROS production concomitant with liver injury. To our knowledge, this is the first report indicating that CYP450 4A and 4F-induced 20-HETE production mediates reactive oxygen species overgeneration in Hbbth3/+ mice through an NADPH-dependent pathway.

Medicinal Plants and Phytochemicals Regulating Insulin Resistance and Glucose Homeostasis in Type 2 Diabetic Patients: A Clinical Review

Diabetes is a major health problem affecting more than four hundred million adults worldwide. The transition from normal glucose tolerance to type 2 diabetes (T2D) is preceded by increased Insulin resistance (IR), an independent predictor of the development of T2D in high risk (e.g. obese populations, pre-diabetes) individuals. Insulin deficiency resulting from increased IR results in progressive glucose homeostasis dysfunction. Data has shown that IR is affected by many different factors such as genetics, age, exercise, dietary nutrients, obesity, and body fat distribution. One of the most important factors is diet, which plays an essential role in addressing T2D and metabolic syndrome. Nutraceuticals and medicinal plants have been shown to have efficacy in preventing chronic diseases like cancer, non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, diabetes mellitus and metabolic syndrome, likely through the anti-inflammatory properties found in nutraceuticals. However, the effect of these compounds, including traditional plant medicines, herbal formulations or their extracts on IR have not been systematically investigated. The objective of this review was to assess the reported effects of medicinal plants and bioactive natural compounds on IR. The findings confirm that most of the herbal bioactive compounds including resveratrol, garlic, curcumin, cinnamon, ginger, nuts, berberine, anthocyanin, soybean, flaxseed, vegetable oils, and soluble fibers have benefit in their efficacy for decreasing IR, fasting blood sugar (FBS), fasting insulin and HbA1c.

Effects of thiamine and fenofibrate on high glucose and hypoxia-induced damage in cell models of the inner blood-retinal barrier

AIMS

Although diabetic retinopathy has long been considered a microvascular complication, retinal neurodegeneration and inflammation may precede its clinical manifestations. Despite all research efforts, the primary treatment options remain laser photocoagulation and anti-vascular endothelial growth factor (VEGF) intravitreal injections, both aggressive and targeting the late stages of the disease. Medical treatments addressing the early phases of diabetic retinopathy are therefore needed. We aimed at verifying if thiamine and fenofibrate protect the cells of the inner blood-retinal barrier from the metabolic stress induced by diabetic-like conditions.

METHODS

Human microvascular endothelial cells (HMECs), retinal pericytes (HRPs) and Müller cells (MIO-M1) were cultured in intermittent high glucose (intHG) and/or hypoxia, with addition of fenofibrate or thiamine. Modulation of adhesion molecules and angiogenic factors was addressed.

RESULTS

Integrins β1/αVβ3 and ICAM1 were upregulated in HMECs/HRPs cultured in diabetic-like conditions, as well as metalloproteases MMP2/9 in HRP, with a reduction in their inhibitor TIMP1; MMP2 increased also in HMEC, and TIMP1 decreased in MIO-M1. VEGF and HIF-1α were strongly increased in HMEC in intHG + hypoxia, and VEGF also in HRP. Ang-1/2 augmented in HMEC/MIO-M1, and MCP-1 in HRP/MIO-M1 in intHG + hypoxia. Thiamine was able to normalize all such abnormal modulations, while fenofibrate had effects in few cases only.

CONCLUSIONS

We suggest that endothelial cells and pericytes are more affected than Müller cells by diabetic-like conditions. Fenofibrate shows a controversial behavior, potentially positive on Müller cells and pericytes, but possibly detrimental to endothelium, while thiamine confirms once more to be an effective agent in reducing diabetes-induced retinal damage.

(5-Hydroxy-4-oxo-2-styryl-4H-pyridin-1-yl)-acetic Acid Derivatives as Multifunctional Aldose Reductase Inhibitors

As rate-limited enzyme of polyol pathway, aldose reductase (ALR2) is one of the key inhibitory targets for alleviating diabetic complications. To reduce the toxic side effects of the inhibitors and to decrease the level of oxidative stress, the inhibitory selectivity towards ALR2 against detoxicating aldehyde reductase (ALR1) and antioxidant activity are included in the design of multifunctional ALR2 inhibitors. Hydroxypyridinone derivatives were designed, synthesized and evaluated their inhibitory behavior and antioxidant activity. Notably, {2-[2-(3,4-dihydroxy-phenyl)-vinyl]-5-hydroxy-4-oxo-4H-pyridin-1-yl}-acetic acid (7l) was the most potent, with IC₅₀ values of 0.789 μM. Moreover, 7l showed excellent selectivity towards ALR2 with selectivity index 25.23, which was much higher than that of eparlestat (17.37), the positive control. More significantly, 7l performed powerful antioxidative action. At a concentration of 1 μM, phenolic compounds 7l scavenged DPPH radical with an inhibitory rate of 41.48%, which was much higher than that of the well-known antioxidant Trolox, at 11.89%. Besides, 7l remarkably suppressed lipid peroxidation with a rate of 88.76% at a concentration of 100 μM. The binding mode derived from molecular docking proved that the derivatives were tightly bound to the activate site, suggesting strongly inhibitory action of derivatives against ALR2. Therefore, these results provided an achievement of multifunctional ALR2 inhibitors capable with potency for both selective ALR2 inhibition and as antioxidants.

Dihydrobenzoxazinone derivatives as aldose reductase inhibitors with antioxidant activity

Dihydrobenzoxazinone based design and synthesis produced two series of compounds as aldose reductase (ALR2) inhibitor candidates. In particular, phenolic residues were embodied into the compounds for the combination of strengthening the inhibitory acitvity and antioxidant ability to retard the progression of diabetic complications. Most of the derivatives with styryl side chains exhibited excellent activities on selective ALR2 inhibition with IC₅₀ values ranging from 0.082 to 0.308 μM, and {8-[2-(4-hydroxy-phenyl)-vinyl]-2-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl}-acetic acid (3a) was the most potent. More significantly, most of dihydrobenzoxazinone compounds revealed not only good inhibitory effect on ALR2, but also showed powerful antioxidant activity. Notably, phenolic compound 3a was even comparable to the well-known antioxidant Trolox, confirming that the C8 p-hydroxystyryl substitution was key structure of lowering oxidative stress. Therefore, these results provided an achievement of multifunctional ALR2 inhibitors possessing capacities for both ALR2 inhibition and as antioxidants.

Promising Anti-stroke Signature of Voglibose: Investigation through In- Silico Molecular Docking and Virtual Screening in In-Vivo Animal Studies

Background:

Postprandial hyperglycemia considered to be a major risk factor for cerebrovascular complications.

Objective:

The current study was designed to elucidate the beneficial role of voglibose via in-silico in vitro to in-vivo studies in improving the postprandial glycaemic state by protection against strokeprone type 2 diabetes.

Material and Methods:

In-Silico molecular docking and virtual screening were carried out with the help of iGEMDOCK+ Pymol+docking software and Protein Drug Bank database (PDB). Based on the results of docking studies, in-vivo investigation was carried out for possible neuroprotective action. T2DM was induced by a single injection of streptozotocin (90mg/kg, i.v.) to neonates. Six weeks after induction, voglibose was administered at the dose of 10mg/kg p.o. for two weeks. After eight weeks, diabetic rats were subjected to middle cerebral artery occlusion, and after 72 hours of surgery, neurological deficits were determined. The blood was collected for the determination of serum glucose, CK-MB, LDH and lipid levels. Brains were excised for determination of brain infarct volume, brain hemisphere weight difference, Na+-K+ ATPase activity, ROS parameters, NO levels, and aldose reductase activity.

Results:

In-silico docking studies showed good docking binding score for stroke associated proteins, which possibly hypotheses neuroprotective action of voglibose in stroke. In the present in-vivo study, pre-treatment with voglibose showed a significant decrease (p<0.05) in serum glucose and lipid levels. Voglibose has shown significant (p<0.05) reduction in neurological score, brain infarct volume, the difference in brain hemisphere weight. On biochemical evaluation, treatment with voglibose produced significant (p<0.05) decrease in CK-MB, LDH, and NO levels in blood and reduction in Na+-K+ ATPase, oxidative stress, and aldose reductase activity in brain homogenate.

Conclusion:

In-silico molecular docking and virtual screening studies and in-vivo studies in MCAo induced stroke, animal model outcomes support the strong anti-stroke signature for possible neuroprotective therapeutics.

Identification of QTLs Controlling α-Glucosidase Inhibitory Activity in Pepper (Capsicum annuum L.) Leaf and Fruit Using Genotyping-by-Sequencing Analysis

Diabetes mellitus, a group of metabolic disorders characterized by hyperglycemia, is one of the most serious and common diseases around the world and is associated with major complications such as diabetic neuropathy, retinopathy, and cardiovascular diseases. A widely used treatment for non-insulin-dependent diabetes is α-glucosidase inhibitors (AGIs) such as acarbose, which hinders hydrolytic cleavage of disaccharides and retard glucose absorption. The ability to inhibit α-glucosidase activity has been reported in leaf and fruit of pepper (Capsicum annuum L.). In this study, we aimed to identify quantitative trait loci (QTLs) controlling α-glucosidase inhibitory activity (AGI activity) in pepper leaf and fruit using enzyme assay and genotyping-by-sequencing (GBS) analysis. The AGI activity at three stages of leaf and one stage of fruit development was analyzed by 96 F2 individuals. GBS analysis identified 17,427 SNPs that were subjected to pepper genetic linkage map construction. The map, consisting of 763 SNPs, contained 12 linkage groups with a total genetic distance of 2379 cM. QTL analysis revealed seven QTLs (qAGI1.1, qAGI11.1, qAGI5.1, qAGI9.1, qAGI12.1, qAGI5.2, and qAGI12.2) controlling AGI activity in pepper leaf and fruit. The QTLs for AGI activity varied by plant age and organ. This QTL information is expected to provide a significant contribution to developing pepper varieties with high AGI activity.

The role of reactive oxygen species in the pathogenesis and treatment of retinal diseases

Reactive oxygen species (ROS) normally play an important physiological role in health regulating cellular processes and signal transduction. The amount of ROS is usually kept in fine balance with the generation of ROS largely being offset by the body's antioxidants. A tipping of this balance has increasingly been recognised as a contributor to human disease. The retina, as a result of its cellular anatomy and physical location, is a potent generator of ROS that has been linked to several major retinal diseases. This review will provide a summary of the role of oxidative stress in the pathogenesis of diabetic retinopathy, age-related macular degeneration, myopia, retinal vein occlusion, retinitis pigmentosa and retinopathy of prematurity. Therapies aimed at controlling oxidative stress in these diseases are also examined.

High Glucose Affects the Cytotoxic Potential of Rapamycin, Metformin and Hydrogen Peroxide in Cultured Human Mesenchymal Stem Cells

BACKGROUND

Oxidative stress and chronic hyperglycemia are two major side effects of type 2 diabetes affecting all cell types including mesenchymal stem cells (MSCs). As a cell therapy choice, understanding the behavior of MSCs will provide crucial information for efficient treatment.

METHODS

Placental mesenchymal stem cells were treated with various concentrations of glucose, metformin, rapamycin, and hydrogen peroxide to monitor their viability and cell cycle distribution. Cellular viability was examined via the MTT assay. Cell cycle distribution was studied by propidium iodide staining and apoptosis was determined using Annexin Vpropidium iodide staining and flow cytometry. Involvement of potential signaling pathways was evaluated by Western blotting for activation of Akt, P70S6K, and AMPK.

RESULTS

The results indicated that high glucose augmented cell viability and reduced metformin toxic potential. However, the hydrogen peroxide and rapamycin toxicities were exacerbated.

CONCLUSION

Our findings suggest that high glucose concentration has a major effect on placental mesenchymal stem cell viability in the presence of rapamycin, metformin and hydrogen peroxide in culture.

Oxidative Stress and Vascular Dysfunction in the Retina: Therapeutic Strategies

Many retinal diseases, such as diabetic retinopathy, glaucoma, and age-related macular (AMD) degeneration, are associated with elevated reactive oxygen species (ROS) levels. ROS are important intracellular signaling molecules that regulate numerous physiological actions, including vascular reactivity and neuron function. However, excessive ROS formation has been linked to vascular endothelial dysfunction, neuron degeneration, and inflammation in the retina. ROS can directly modify cellular molecules and impair their function. Moreover, ROS can stimulate the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) causing inflammation and cell death. However, there are various compounds with direct or indirect antioxidant activity that have been used to reduce ROS accumulation in animal models and humans. In this review, we report on the physiological and pathophysiological role of ROS in the retina with a special focus on the vascular system. Moreover, we present therapeutic approaches for individual retinal diseases targeting retinal signaling pathways involving ROS.

Shaping Up Mitochondria in Diabetic Nephropathy

Mitochondrial medicine has experienced significant progress in recent years and is expected to grow significantly in the near future, yielding many opportunities to translate novel bench discoveries into clinical medicine. Multiple lines of evidence have linked mitochondrial dysfunction to a variety of metabolic diseases, including diabetic nephropathy (DN). Mitochondrial dysfunction presumably precedes the emergence of key histologic and biochemical features of DN, which provides the rationale to explore mitochondrial fitness as a novel therapeutic target in patients with DN. Ultimately, the success of mitochondrial medicine is dependent on a better understanding of the underlying biology of mitochondrial fitness and function. To this end, recent advances in mitochondrial biology have led to new understandings of the potential effect of mitochondrial dysfunction in a myriad of human pathologies. We have proposed that molecular mechanisms that modulate mitochondrial dynamics contribute to the alterations of mitochondrial fitness and progression of DN. In this comprehensive review, we highlight the possible effects of mitochondrial dysfunction in DN, with the hope that targeting specific mitochondrial signaling pathways may lead to the development of new drugs that mitigate DN progression. We will outline potential tools to improve mitochondrial fitness in DN as a novel therapeutic strategy. These emerging views suggest that the modulation of mitochondrial fitness could serve as a key target in ameliorating progression of kidney disease in patients with diabetes.

Retinal Physiology and Circulation: Effect of Diabetes

In this article, we present a discussion of diabetes and its complications, including the macrovascular and microvascular effects, with the latter of consequence to the retina. We will discuss the anatomy and physiology of the retina, including aspects of metabolism and mechanisms of oxygenation, with the latter accomplished via a combination of the retinal and choroidal blood circulations. Both of these vasculatures are altered in diabetes, with the retinal circulation intimately involved in the pathology of diabetic retinopathy. The later stages of diabetic retinopathy involve poorly controlled angiogenesis that is of great concern, but in our discussion, we will focus more on several alterations in the retinal circulation occurring earlier in the progression of disease, including reductions in blood flow and a possible redistribution of perfusion that may leave some areas of the retina ischemic and hypoxic. Finally, we include in this article a more recent area of investigation regarding the diabetic retinal vasculature, that is, the alterations to the endothelial surface layer that normally plays a vital role in maintaining physiological functions. © 2020 American Physiological Society. Compr Physiol 10:933-974, 2020.

High Concentrations of Uric Acid and Angiotensin II Act Additively to Produce Endothelial Injury

Renin angiotensin (Ang) system (RAS) activation in metabolic syndrome (MS) patients is associated with elevated uric acid (UA) levels, resulting in endothelial system dysfunction. Our previous study demonstrated that excessive UA could cause endothelial injury through the aldose reductase (AR) pathway. This study is the first to show that a high concentration of Ang II in human umbilical vein endothelial cells (HUVECs) increases reactive oxygen species (ROS) components, including O₂^·- and H₂O₂, and further aggravates endothelial system injury induced by high UA (HUA). In a MS/hyperuricemia model, nitric oxide (NO) production was decreased, followed by a decrease in total antioxidant capacity (TAC), and the concentration of the endothelial injury marker von Willebrand factor (vWF) in the serum was increased. Treatment with catalase and polyethylene glycol covalently linked to superoxide dismutase (PEG-SOD) to individually remove H₂O₂ and O₂^·- or treatment with the AR inhibitor epalrestat decreased ROS and H₂O₂, increased NO levels and TAC, and reduced vWF release. Taken together, these data indicate that HUA and Ang II act additively to cause endothelial dysfunction via oxidative stress, and specific elimination of O₂^·- and H₂O₂ improves endothelial function. We provide theoretical evidence to prevent or delay endothelial injury caused by metabolic diseases.