Aldose Reductase: a cause and a potential target for the treatment of diabetic complications

Effects of Reactive Oxygen and Nitrogen Species on Male Fertility

Significance: In recent decades, male fertility has been severely reduced worldwide. The causes underlying this decline are multifactorial, and include, among others, genetic alterations, changes in the microbiome, and the impact of environmental pollutants. Such factors can dysregulate the physiological levels of reactive species of oxygen (ROS) and nitrogen (RNS) in the patient, generating oxidative and nitrosative stress that impairs fertility. Recent Advances: Recent studies have delved into other factors involved in the dysregulation of ROS and RNS levels, such as diet, obesity, persistent infections, environmental pollutants, and gut microbiota, thus leading to new strategies to solve male fertility problems, such as consuming prebiotics to regulate gut flora or treating psychological conditions. Critical Issues: The pathways where ROS or RNS may be involved as modulators are still under investigation. Moreover, the extent to which treatments can rescue male infertility as well as whether they may have side effects remains, in most cases, to be elucidated. For example, it is known that prescription of antioxidants to treat nitrosative stress can alter sperm chromatin condensation, which makes DNA more exposed to ROS and RNS, and may thus affect fertilization and early embryo development. Future Directions: The involvement of extracellular vesicles, which might play a crucial role in cell communication during spermatogenesis and epididymal maturation, and the relevance of other factors such as sperm epigenetic signatures should be envisaged in the future.

TEAD1, MYO7A and NDUFC2 are novel functional genes associated with glucose metabolism in BXD recombinant inbred population

AIM

The liver is an important metabolic organ that governs glucolipid metabolism, and its dysfunction may cause non-alcoholic fatty liver disease, type 2 diabetes mellitus, dyslipidaemia, etc. We aimed to systematic investigate the key factors related to hepatic glucose metabolism, which may be beneficial for understanding the underlying pathogenic mechanisms for obesity and diabetes mellitus.

MATERIALS AND METHODS

Oral glucose tolerance test (OGTT) phenotypes and liver transcriptomes of BXD mice under chow and high-fat diet conditions were collected from GeneNetwork. QTL mapping was conducted to pinpoint genomic regions associated with glucose homeostasis. Candidate genes were further nominated using a multi-criteria approach and validated to confirm their functional relevance in vitro.

RESULTS

Our results demonstrated that plasma glucose levels in OGTT were significantly affected by both diet and genetic background, with six genetic regulating loci were mapped on chromosomes 1, 4, and 7. Moreover, TEAD1, MYO7A and NDUFC2 were identified as the candidate genes. Functionally, siRNA-mediated TEAD1, MYO7A and NDUFC2 knockdown significantly decreased the glucose uptake and inhibited the transcription of genes related to insulin and glucose metabolism pathways.

CONCLUSIONS

Our study contributes novel insights to the understanding of hepatic glucose metabolism, demonstrating the impact of TEAD1, MYO7A and NDUFC2 on mitochondrial function in the liver and their regulatory role in maintaining in glucose homeostasis.

Structure-based virtual screening of mangiferin derivatives with antidiabetic action: a molecular docking and dynamics study and MPO-based drug-likeness approach

Extracts from Mangifera indica leaves and its main component, mangiferin, have proven antidiabetic activity. In this study, mangiferin and its natural derivatives Homomangiferin (HMF), Isomangiferin (IMF), Neomangiferin (NMF), Glucomangiferin (GMF), Mangiferin 6'-gallate (MFG), and Norathyriol (NRT) were compared regarding their action on Diabetes mellitus (DM), employing docking and molecular dynamics (MD) simulations to analyze interactions with the aldose reductase enzyme, the precursor to the conversion of glucose into sorbitol. Notably, HMF showed significant affinity to residues in the active site of the enzyme, including Trp 79, His 110, Trp 111, Phe 122, and Phe 300, with an energy of - 7.2 kcal/mol, observed in the molecular docking simulations. MD reinforced the formation of stable complexes for HMF and MFG with the aldose reductase, with interaction potential energies (IPE) in the order of - 300.812 ± 52 kJ/mol and - 304.812 ± 52 kJ/mol, respectively. The drug-likeness assessment, by multiparameter optimization (MPO), highlighted that HMF and IMF have similarities with polyphenols and glycosidic flavonoids recently patented as antidiabetics, revealing that high polarity (TPSA > 180 Å2) is a favorable property for subcutaneous administration, especially because of the gradual passive cell permeability values in biological tissues, with Papp values estimated at < 10 × 10-6 cm/s. These compounds are metabolically stable against metabolic enzymes, resulting in a low toxic incidence by metabolic activation, corroborating with a lethal dose (LD50) greater than 2000 mg/kg. In this way, HMF showed a systematic alignment between predicted pharmacokinetics and pharmacodynamics, characterizing it as the most favorable substance for inhibiting aldose reductase.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03978-9.

High incidence of sebaceous gland inflammation in aldose reductase-deficient mice

Aldose reductase is a member of the 1B1 subfamily of aldo-keto reductase gene superfamily. The action of aldose reductase (AR) has been implicated in the pathogenesis of a variety of disease states, most notably complications of diabetes mellitus including neuropathy, retinopathy, nephropathy, and cataracts. To explore for mechanistic roles for AR in disease pathogenesis, we established mutant strains produced using Crispr-Cas9 to inactivate the AKR1B3 gene in C57BL6 mice. Phenotyping AR-knock out (ARKO) strains confirmed previous reports of reduced accumulation of tissue sorbitol levels. Lens epithelial cells in ARKO mice showed markedly reduced epithelial-to-mesenchymal transition following lens extraction in a surgical model of cataract and posterior capsule opacification. A previously unreported phenotype of preputial sebaceous gland swelling was observed frequently in male ARKO mice homozygous for the mutant AKR1B3 allele. This condition, which was shown to be accompanied by infiltration of proinflammatory CD3+ lymphocytes, was not observed in WT mice or mice heterozygous for the mutant allele. Despite this condition, reproductive fitness of the ARKO strain was indistinguishable from WT mice housed under identical conditions. These studies establish the utility of a new strain of AKR1B3-null mice created to support mechanistic studies of cataract and diabetic eye disease.

Novel spiroindoline derivatives targeting aldose reductase against diabetic complications: Bioactivity, cytotoxicity, and molecular modeling studies

Despite significant developments in therapeutic strategies, Diabetes Mellitus remains an increasing concern, leading to various complications, e.g., cataracts, neuropathy, retinopathy, nephropathy, and several cardiovascular diseases. The polyol pathway, which involves Aldose reductase (AR) as a critical enzyme, has been focused on by many researchers as a target for intervention. On the other hand, spiroindoline-based compounds possess remarkable biological properties. This guided us to synthesize novel spiroindoline oxadiazolyl-based acetate derivatives and investigate their biological activities. The synthesized molecules' structures were confirmed herein, using IR, NMR (1H and 13C), and Mass spectroscopy. All compounds were potent inhibitors with KI constants spanning from 0.186 ± 0.020 μM to 0.662 ± 0.042 μM versus AR and appeared as better inhibitors than the clinically used drug, Epalrestat (EPR, KI: 0.841 ± 0.051 μM). Besides its remarkable inhibitory profile compared to EPR, compound 6k (KI: 0.186 ± 0.020 μM) was also determined to have an unusual pharmacokinetic profile. The results showed that 6k had less cytotoxic effect on normal mouse fibroblast (L929) cells (IC50 of 569.58 ± 0.80 μM) and reduced the viability of human breast adenocarcinoma (MCF-7) cells (IC50 of 110.87 ± 0.42 μM) more than the reference drug Doxorubicin (IC50s of 98.26 ± 0.45 μM and 158.49 ± 2.73 μM, respectively), thus exhibiting more potent anticancer activity. Moreover, molecular dynamic simulations for 200 ns were conducted to predict the docked complex's stability and reveal significant amino acid residues that 6k interacts with throughout the simulation.

Research progress of the effective active ingredients of Astragalus mongholicus in the treatment of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most prevalent consequences of diabetes, with a high incidence and disability rate. The DPN's pathogenesis is extremely complex and yet to be fully understood. Persistent high glucose metabolism, nerve growth factor deficiency, microvascular disease, oxidative stress, peripheral nerve cell apoptosis, immune factors, and other factors have been implicated in the pathogenesis of DPN. Astragalus mongholicus is a commonly used plant used to treat DPN in clinical settings. Its rich chemical components mainly include Astragalus polysaccharide, Astragalus saponins, Astragalus flavones, etc., which play a vital role in the treatment of DPN. This review aimed to summarize the pathogenesis of DPN and the studies on the mechanism of the effective components of Astragalus mongholicus in treating DPN. This is of great significance for the effective use of Chinese herbal medicine and the promotion of its status and influence on the world.

How inflammation dictates diabetic peripheral neuropathy: An enlightening review

BACKGROUND

Diabetic peripheral neuropathy (DPN) constitutes a debilitating complication associated with diabetes. Although, the past decade has seen rapid developments in understanding the complex etiology of DPN, there are no approved therapies that can halt the development of DPN, or target the damaged nerve. Therefore, clarifying the pathogenesis of DPN and finding effective treatment are the crucial issues for the clinical management of DPN.

AIMS

This review is aiming to summary the current knowledge on the pathogenesis of DPN, especially the mechanism and application of inflammatory response.

METHODS

We systematically summarized the latest studies on the pathogenesis and therapeutic strategies of diabetic neuropathy in PubMed.

RESULTS

In this seminal review, the underappreciated role of immune activation in the progression of DPN is scrutinized. Novel insights into the inflammatory regulatory mechanisms of DPN have been unearthed, illuminating potential therapeutic strategies of notable clinical significance. Additionally, a nuanced examination of DPN's complex etiology, including aberrations in glycemic control and insulin signaling pathways, is presented. Crucially, an emphasis has been placed on translating these novel understandings into tangible clinical interventions to ameliorate patient outcomes.

CONCLUSIONS

This review is distinguished by synthesizing cutting-edge mechanisms linking inflammation to DPN and identifying innovative, inflammation-targeted therapeutic approaches.

Decoding selectivity: computational insights into AKR1B1 and AKR1B10 inhibition

Understanding selectivity mechanisms of inhibitors towards highly homologous proteins is of paramount importance in the design of selective candidates. Human aldo-keto reductases (AKRs) pertain to a superfamily of monomeric oxidoreductases, which serve as NADPH-dependent cytosolic enzymes to catalyze the reduction of carbonyl groups to primary and secondary alcohols using electrons from NADPH. Among AKRs, AKR1B1 is emerging as a promising target for cancer treatment and diabetes, despite its high structural similarity with AKR1B10, which leads to severe adverse events. Therefore, it is crucial to understand the selectivity mechanisms of AKR1B1 and AKR1B10 to discover safe anticancer candidates with optimal therapeutic efficacy. In this study, multiple computational strategies, including sequence alignment, structural comparison, Protein Contacts Atlas analysis, molecular docking, molecular dynamics simulation, MM-GBSA calculation, alanine scanning mutagenesis and pharmacophore modeling analysis were employed to comprehensively understand the selectivity mechanisms of AKR1B1/10 inhibition based on selective inhibitor lidorestat and HAHE. This study would provide substantial evidence in the design of potent and highly selective AKR1B1/10 inhibitors in future.

Cell metabolism pathways involved in the pathophysiological changes of diabetic peripheral neuropathy

Diabetic peripheral neuropathy is a common complication of diabetes mellitus. Elucidating the pathophysiological metabolic mechanism impels the generation of ideal therapies. However, existing limited treatments for diabetic peripheral neuropathy expose the urgent need for cell metabolism research. Given the lack of comprehensive understanding of energy metabolism changes and related signaling pathways in diabetic peripheral neuropathy, it is essential to explore energy changes and metabolic changes in diabetic peripheral neuropathy to develop suitable treatment methods. This review summarizes the pathophysiological mechanism of diabetic peripheral neuropathy from the perspective of cellular metabolism and the specific interventions for different metabolic pathways to develop effective treatment methods. Various metabolic mechanisms (e.g., polyol, hexosamine, protein kinase C pathway) are associated with diabetic peripheral neuropathy, and researchers are looking for more effective treatments through these pathways.

Recent advances in the treatment and delivery system of diabetic retinopathy

Diabetic retinopathy (DR) is a highly tissue-specific neurovascular complication of type 1 and type 2 diabetes mellitus and is among the leading causes of blindness worldwide. Pathophysiological changes in DR encompass neurodegeneration, inflammation, and oxidative stress. Current treatments for DR, including anti-vascular endothelial growth factor, steroids, laser photocoagulation, and vitrectomy have limitations and adverse reactions, necessitating the exploration of novel treatment strategies. This review aims to summarize the current pathophysiology, therapeutic approaches, and available drug-delivery methods for treating DR, and discuss their respective development potentials. Recent research indicates the efficacy of novel receptor inhibitors and agonists, such as aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, peroxisome proliferator-activated receptor alpha agonists, and novel drugs in delaying DR. Furthermore, with continuous advancements in nanotechnology, a new form of drug delivery has been developed that can address certain limitations of clinical drug therapy, such as low solubility and poor penetration. This review serves as a theoretical foundation for future research on DR treatment. While highlighting promising therapeutic targets, it underscores the need for continuous exploration to enhance our understanding of DR pathogenesis. The limitations of current treatments and the potential for future advancements emphasize the importance of ongoing research in this field.

Biological Activities of Secondary Metabolites from the Edible-Medicinal Macrofungi

Macrofungi are well-known as edible-medicinal mushrooms, which belong mostly to Basidiomycota, with a few from Ascomycota. In recent years, macrofungi have been recognized as a rich resource of structurally unique secondary metabolites, demonstrating a wide range of bioactivities, including anti-tumor, antioxidant, anti-inflammatory, antimicrobial, antimalarial, neuro-protective, hypoglycemic, and hypolipidemic activities. This review highlights over 270 natural products produced by 17 families of macrofungi covering 2017 to 2023, including their structures, bioactivities, and related molecular mechanisms.

Proteomics-based screening of AKR1B1 as a therapeutic target and validation study for sepsis-associated acute kidney injury

Background

Sepsis and sepsis-associated acute kidney injury (SA-AKI) pose significant global health challenges, necessitating the development of innovative therapeutic strategies. Dysregulated protein expression has been implicated in the initiation and progression of sepsis and SA-AKI. Identifying potential protein targets and modulating their expression is crucial for exploring alternative therapies.

Method

We established an SA-AKI rat model using cecum ligation perforation (CLP) and employed differential proteomic techniques to identify protein expression variations in kidney tissues. Aldose reductase (AKR1B1) emerged as a promising target. The SA-AKI rat model received treatment with the aldose reductase inhibitor (ARI), epalrestat. Blood urea nitrogen (BUN) and creatinine (CRE) levels, as well as IL-1β, IL-6 and TNF-α levels in the serum and kidney tissues, were monitored. Hematoxylin-eosin (H-E) staining and a pathological damage scoring scale assessed renal tissue damage, while protein blotting determined PKC (protein kinase C)/NF-κB pathway protein expression.

Result

Differential proteomics revealed significant downregulation of seven proteins and upregulation of 17 proteins in the SA-AKI rat model renal tissues. AKR1B1 protein expression was notably elevated, confirmed by Western blot. ARI prophylactic administration and ARI treatment groups exhibited reduced renal injury, low BUN and CRE levels and decreased IL-1β, IL-6 and TNF-α levels compared to the CLP group. These changes were statistically significant (P < 0.05). AKR1B1, PKC-α, and NF-κB protein expression levels were also lowered in the ARI prophylactic administration and ARI treatment groups compared to the CLP group (P < 0.05).

Conclusions

Epalrestat appeared to inhibit the PKC/NF-κB inflammatory pathway by inhibiting AKR1B1, resulting in reduced inflammatory cytokine levels in renal tissues and blood. This mitigated renal tissue injuries and improved the systemic inflammatory response in the severe sepsis rat model. Consequently, AKR1B1 holds promise as a target for treating sepsis-associated acute kidney injuries.

Symbiotic Antidiabetic Effect of Lactobacillus casei and the Bioactive Extract of Cleome droserifolia (Forssk.) Del. on Mice with Type 2 Diabetes Induced by Alloxan

The consumption of probiotics protects pancreatic β-cells from oxidative damage, delaying the onset of type 2 diabetes mellitus (T2DM) and preventing microvascular and macrovascular complications. This study aimed to evaluate the antidiabetic activity of CDE fermented by Lactobacillus casei (ATCC 39539) (LC) in alloxan-induced diabetic rats. The oxidative stress identified by catalase (CAT), serum AST, ALT, ALP, creatinine, urea, and uric acid were measured. The chemical profiles of the plant extract and the fermented extract were studied using HPLC/MS. The potential of the compounds towards the binding pockets of aldose reductase and PPAR was discovered by molecular docking. A significant reduction in fasting blood glucose in alloxan-treated rats. The CAT showed a significant decrease in diabetic rats. Also, serum AST, ALT, ALP, creatinine, urea, and uric acid were significantly decreased in the mixture group. Mild histological changes of pancreatic and kidney tissues suggested that the mixture of probiotics and cleome possesses a marked anti-diabetic effect. Overall, the study suggests that the combination of Cleome droserifolia fermented by Lactobacillus casei exhibits significant antidiabetic activity (p-value=0.05), reduces oxidative stress, improves lipid profiles, and shows potential for the treatment of diabetes.

Traditional Chinese medicine for the treatment of immune-related nephropathy: A review

Immune-related nephropathy (IRN) refers to immune-response-mediated glomerulonephritis and is the main cause of end-stage renal failure. The pathogenesis of IRN is not fully understood; therefore, treatment is challenging. Traditional Chinese medicines (TCMs) have potent clinical effects in the treatment of the IRN conditions immunoglobulin A nephropathy, lupus nephropathy, and diabetic nephropathy. The underlying mechanisms mainly include its inhibition of inflammation; improvements to renal interstitial fibrosis, oxidative stress, autophagy, apoptosis; and regulation of immunity. In this review, we summarize the clinical symptoms of the three IRN subtypes and the use of TCM prescriptions, herbs, and bioactive compounds in treating IRN, as well as the potential mechanisms, intending to provide a reference for the future study of TCM as IRN treatments.

Drug screening identifies aldose reductase as a novel target for treating cisplatin-induced hearing loss

Cisplatin is a frequently used chemotherapeutic medicine for cancer treatment. Permanent hearing loss is one of the most serious side effects of cisplatin, but there are few FDA-approved medicines to prevent it. We applied high-through screening and target fishing and identified aldose reductase, a key enzyme of the polyol pathway, as a novel target for treating cisplatin ototoxicity. Cisplatin treatment significantly increased the expression level and enzyme activity of aldose reductase in the cochlear sensory epithelium. Genetic knockdown or pharmacological inhibition of aldose reductase showed a significant protective effect on cochlear hair cells. Cisplatin-induced overactivation of aldose reductase led to the decrease of NADPH/NADP+ and GSH/GSSG ratios, as well as the increase of oxidative stress, and contributed to hair cell death. Results of target prediction, molecular docking, and enzyme activity detection further identified that Tiliroside was an effective inhibitor of aldose reductase. Tiliroside was proven to inhibit the enzymatic activity of aldose reductase via competitively interfering with the substrate-binding region. Both Tiliroside and another clinically approved aldose reductase inhibitor, Epalrestat, inhibited cisplatin-induced oxidative stress and subsequent cell death and thus protected hearing function. These findings discovered the role of aldose reductase in the pathogenesis of cisplatin-induced deafness and identified aldose reductase as a new target for the prevention and treatment of hearing loss.

Discussing pathologic mechanisms of Diabetic retinopathy & therapeutic potentials of curcumin and β-glucogallin in the management of Diabetic retinopathy

Diabetic retinopathy (DR) is a form of retinal microangiopathy that occurs as a result of long-term Diabetes mellitus (DM). Patients with Diabetes mellitus typically suffer from DR as a progression of the disease that may be due to initiation and dysregulation of pathways like the polyol, hexosamine, the AGE/RAGE, and the PKC pathway, which all have negative impacts on eye health and vision. In this review, various databases, including PubMed, Google Scholar, Web of Science, and Science Direct, were scoured for data relevant to the aforementioned title. The three most common therapies for DR today are retinal photocoagulation, anti-vascular endothelial growth factor (VEGF) therapy, and vitrectomy, however, there are a number of drawbacks and limits to these methods. So, it is of critical importance and profound interest to discover treatments that may successfully address the pathogenesis of DR. Curcumin and β-glucogallin are the two potent compounds of natural origin that are already being used in various nutraceutical formulations for several ailments. They have been shown potent antiapoptotic, anti-inflammatory, antioxidant, anticancer, and pro-vascular function benefits in animal experiments. Their parent plant species have been used for generations by practitioners of traditional herbal medicine for the treatment and prevention of various eye ailments. In this review, we will discuss about pathophysiology of Diabetic retinopathy and the therapeutic potentials of curcumin and β-glucogallin one of the principal compounds from Curcuma longa and Emblica officinalis in Diabetic retinopathy.

Sord deficient rats develop a motor-predominant peripheral neuropathy unveiling novel pathophysiological insights

Biallelic SORD mutations cause one of the most frequent forms of recessive hereditary neuropathy, estimated to affect approximately 10,000 patients in North America and Europe alone. Pathogenic SORD loss-of-function changes in the encoded enzyme sorbitol dehydrogenase result in abnormally high sorbitol levels in cells and serum. How sorbitol accumulation leads to peripheral neuropathy remains to be elucidated. A reproducible animal model for SORD neuropathy is essential to illuminate the pathogenesis of SORD deficiency and for preclinical studies of potential therapies. Therefore, we have generated a Sord knockout (KO), Sord -/- , Sprague Dawley rat, to model the human disease and to investigate the pathophysiology underlying SORD deficiency. We have characterized the phenotype in these rats with a battery of behavioral tests as well as biochemical, physiological, and comprehensive histological examinations. Sord -/- rats had remarkably increased levels of sorbitol in serum, cerebral spinal fluid (CSF), and peripheral nerve. Moreover, serum from Sord -/- rats contained significantly increased levels of neurofilament light chain, NfL, an established biomarker for axonal degeneration. Motor performance significantly declined in Sord -/- animals starting at ∼7 months of age. Gait analysis evaluated with video motion tracking confirmed abnormal gait patterns in the hindlimbs. Motor nerve conduction velocities of the tibial nerves were slowed. Light and electron microscopy of the peripheral nervous system revealed degenerating myelinated axons, de- and remyelinated axons, and a likely pathognomonic finding - enlarged "ballooned" myelin sheaths. These findings mainly affected myelinated motor axons; myelinated sensory axons were largely spared. In summary, Sord -/- rats develop a motor-predominant neuropathy that closely resembles the human phenotype. Our studies revealed novel significant aspects of SORD deficiency, and this model will lead to an improved understanding of the pathophysiology and the therapeutic options for SORD neuropathy.

Torachrysone-8-O-β-d-glucoside mediates anti-inflammatory effects by blocking aldose reductase-catalyzed metabolism of lipid peroxidation products

Aldose reductase (AR) is an important enzyme involved in the reduction of various aldehyde and carbonyl compounds, including the highly reactive and toxic 4-hydroxynonenal (4-HNE), which has been linked to the progression of various pathologies such as atherosclerosis, hyperglycemia, inflammation, and tumors. AR inhibitors have potential therapeutic benefits for these diseases by reducing lipid peroxidation and mitigating the harmful effects of reactive aldehydes. In this study, we found that torachrysone-8-O-β-d-glucoside (TG), a natural product isolated from Polygonum multiflorum Thunb., functions as an effective inhibitor of AR, exhibiting potent effects in clearing reactive aldehydes and reducing inflammation. TG up-regulated the mRNA levels of several antioxidant factors downstream of NRF2, especially glutathione S-transferase (GST), which is significantly increased, thus detoxifying 4-HNE by facilitating the conjugation of 4-HNE to glutathione, forming glutathione-4-hydroxynonenal (GS-HNE). By employing a combination of molecular docking, cellular thermal shift assay, and enzyme activity experiments, we demonstrated that TG exhibited strong binding affinity with AR and inhibited its activity and blocked the conversion of GS-HNE to glutathionyl-1,4-dihydroxynonene (GS-DHN), thereby preventing the formation of protein adducts and inducing severe cellular damage. This study provides novel insights into the anti-inflammatory mechanisms of AR inhibitors and offers potential avenues for developing therapeutic strategies for AR-related pathologies. Our findings suggest that TG, as an AR inhibitor, may hold promise as a therapeutic agent for treating conditions characterized by excessive lipid peroxidation and inflammation. Further investigations are needed to fully explore the clinical potential of TG and evaluate its efficacy in the treatment and management of these complex diseases.

Oxidative stress, epigenetic regulation and pathological processes of lens epithelial cells underlying diabetic cataract

Background

Cataract is a blinding disease worldwide. It is an age-related disease that mainly occurs in people over 65 years old. Cataract is also prevalent in patients with diabetes mellites (DM). The pathological mechanisms underlying diabetic cataract (DC) are more complex than that of age-related cataract. Studies have identified that polyol pathway, advanced glycation end products (AGEs) and oxidative stress are the primary pathogenesis of DC. In recent years, molecular-level regulations and pathological processes of lens epithelial cells (LECs) have been confirmed to play roles in the initiation and progression of DC. A comprehensive understanding and elucidation of how chronic hyperglycemia drives molecular-level regulations and cytopathological processes in the lens will shed lights on the prevention, delay and treatment of DC.

Main text

Excessive glucose in the lens enhances polyol pathway and AGEs formation. Polyol pathway causes imbalance in the ratio of NADPH/NADP+ and NADH/NAD+. Decrease in NADPH/NADP+ ratio compromises antioxidant enzymes, while increase in NADH/NAD+ ratio promotes reactive oxygen species (ROS) overproduction in mitochondria, resulting in oxidative stress. Oxidative stress in the lens causes oxidation of DNA, proteins and lipids, leading to abnormalities in their structure and functions. Glycation of proteins by AGEs decreases solubility of proteins. High glucose triggered epigenetic regulations directly or indirectly affect expressions of genes and proteins in LECs. Changes in autophagic activity, increases in fibrosis and apoptosis of LECs destroy the morphological structure and physiological functions of the lens epithelium, disrupting lens homeostasis.

Conclusions

In both diabetic animal models and diabetics, oxidative stress plays crucial roles in the formation of cataract. Epigenetic regulations, include lncRNA, circRNA, microRNA, methylation of RNA and DNA, histone acetylation and pathological processes, include autophagy, fibrosis and apoptosis of LECs also involved in DC.

Potential Defence Mechanisms Triggered by Monosodium Glutamate Sub-Chronic Consumption in Two-Year-Old Wistar Rats

Monosodium glutamate (MSG) is the sodium salt of glutamic acid (GLA), used as a flavour enhancer. MSG is considered a controversial substance. It is incriminated in disturbing the antioxidant system, but also has beneficial effects, as GLA metabolism plays a crucial role in homeostasis. This study highlights which positive or negative aspects of MSG sub-chronic consumption are better reflected in subjects potentially affected by advanced age. Daily doses of MSG were administered to four groups of two-year-old Wistar rats for 90 days: (I) 185 mg/kg bw, (II) 1500 mg/kg bw, (III) 3000 mg/kg bw and (IV) 6000 mg/kg bw, compared to a MSG non-consumer group. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, direct and total bilirubin, total cholesterol, triglycerides, creatinine and urea levels were analysed; stomach, liver and kidney samples were subjected to histopathological analysis. Although, in most cases, there were no statistical differences, interesting aspects of the dose-effect relationship were observed. After MSG sub-chronic consumption, the positive aspects of GLA seem to be reflected better than the negative ones. The hormesis effect, with low-level reactive oxygen species' protective effects and GLA metabolism, may represent the hypothesis of a potential defence mechanism triggered by MSG sub-chronic consumption in ageing rats.

Insights into the liver-eyes connections, from epidemiological, mechanical studies to clinical translation

Maintenance of internal homeostasis is a sophisticated process, during which almost all organs get involved. Liver plays a central role in metabolism and involves in endocrine, immunity, detoxification and storage, and therefore it communicates with distant organs through such mechanisms to regulate pathophysiological processes. Dysfunctional liver is often accompanied by pathological phenotypes of distant organs, including the eyes. Many reviews have focused on crosstalk between the liver and gut, the liver and brain, the liver and heart, the liver and kidney, but with no attention paid to the liver and eyes. In this review, we summarized intimate connections between the liver and the eyes from three aspects. Epidemiologically, we suggest liver-related, potential, protective and risk factors for typical eye disease as well as eye indicators connected with liver status. For molecular mechanism aspect, we elaborate their inter-organ crosstalk from metabolism (glucose, lipid, proteins, vitamin, and mineral), detoxification (ammonia and bilirubin), and immunity (complement and inflammation regulation) aspect. In clinical application part, we emphasize the latest advances in utilizing the liver-eye axis in disease diagnosis and therapy, involving artificial intelligence-deep learning-based novel diagnostic tools for detecting liver disease and adeno-associated viral vector-based gene therapy method for curing blinding eye disease. We aim to focus on and provide novel insights into liver and eyes communications and help resolve existed clinically significant issues.

A dual-acting aldose reductase inhibitor impedes oxidative and carbonyl stress in tissues of fructose- and streptozotocin-induced rats: comparison with antioxidant stobadine

Inhibiting aldose reductase (ALR2, AR) as well as maintaining a concomitant antioxidant (AO) activity via dual-acting agents may be a rational approach to prevent cellular glucotoxicity and at least delay the progression of diabetes mellitus (DM). This study was aimed at evaluating the dual-acting AR inhibitor (ARI) cemtirestat (CMTI) on tissue oxidative stress (OS) and carbonyl stress (CS) biomarkers in rats exposed to fructose alone (F) or fructose plus streptozotocin (D; type-2 diabetic). D and F rats were either untreated or treated daily with low- or high-dose CMTI, ARI drug epalrestat (EPA) or antioxidant stobadine (STB) for 14 weeks. Malondialdehyde (MDA), glutathione S-transferase (GST), nitric oxide synthase (NOS), and catalase (CAT) were increased in the sciatic nerve of F and D. These increases were attenuated by low doses of CMTI and STB in D, but exacerbated by low-dose EPA and high-dose CMTI in F. STB and CMTI and to a lesser extent EPA improved MDA, protein-carbonyl, GST and CAT in the hearts and lungs of F and D. CMTI and STB were more effective than EPA in improving the increased MDA and protein-carbonyl levels in the kidneys of F and especially D. CMTI ameliorated renal GST inhibition in D. In the lungs, hearts, and kidneys of F and D, the GSH to GSSG ratio decreased and caspase-3 activity increased, but partially resolved with treatments. In conclusion, CMTI with ARI/AO activity may be advantageous in overcoming OS, CS, and their undesirable consequences, with low dose efficacy and limited toxicity, compared to ARI or antioxidant alone.

Natural Bioactive Compounds from Marine Invertebrates That Modulate Key Targets Implicated in the Onset of Type 2 Diabetes Mellitus (T2DM) and Its Complications

BACKGROUND

Type 2 diabetes mellitus (T2DM) is an ongoing, risky, and costly health problem that therefore always requires new treatment options. Moreover, although several drugs are available, only 36% of patients achieve glycaemic control, and patient adherence is a major obstacle. With monotherapy, T2DM and its comorbidities/complications often cannot be managed, and the concurrent administration of several hypoglycaemic drugs is required, which increases the risk of side effects. In fact, despite the efficacy of the drugs currently on the market, they generally come with serious side effects. Therefore, scientific research must always be active in the discovery of new therapeutic agents.

DISCUSSION

The present review highlights some of the recent discoveries regarding marine natural products that can modulate the various targets that have been identified as crucial in the establishment of T2DM disease and its complications, with a focus on the compounds isolated from marine invertebrates. The activities of these metabolites are illustrated and discussed.

OBJECTIVES

The paper aims to capture the relevant evidence of the great chemical diversity of marine natural products as a key tool that can advance understanding in the T2DM research field, as well as in antidiabetic drug discovery. The variety of chemical scaffolds highlighted by the natural hits provides not only a source of chemical probes for the study of specific targets involved in the onset of T2DM, but is also a helpful tool for the development of drugs that are capable of acting via novel mechanisms. Thus, it lays the foundation for the design of multiple ligands that can overcome the drawbacks of polypharmacology.

Eucommia lignans alleviate the progression of diabetic nephropathy through mediating the AR/Nrf2/HO-1/AMPK axis in vivo and in vitro

Lignans derived from Eucommia ulmoides Oliver (Eucommia lignans) inhibit the progression of inflammatory diseases, while their effect on the progression of diabetic nephropathy (DN) remained unclear. This work was designed to assess the function of Eucommia lignans in DN. The major constituents of Eucommia lignans were analyzed by UPLC-Q-TOF-MS/MS. The binding between Eucommia lignans and aldose reductase (AR) was predicted by molecular docking. Eucommia lignans (200, 100, and 50 mg·kg^-1) were used in model animals to evaluate their renal function changes. Rat glomerular mesangial cells (HBZY-1) were transfected with sh-AR, sh-AMPK, and oe-AR in the presence of high glucose (HG) or HG combined with Eucommia lignans to evaluate whether Eucommia lignans affected HG-induced cell injury and mitochondrial dysfunction through the AR/Nrf2/HO-1/AMPK axis. Eucommia lignans significantly attenuated the progression of DN in vivo. Eucommia lignans notably reversed HG-induced upregulation of inflammatory cytokines and mitochondrial injury, while downregulating the levels of Cyto c, caspase 9, AR, and NOX4 in HBZY-1 cells. In contrast, HG-induced downregulation of Nrf2, HO-1 and p-AMPKα levels were abolished by Eucommia lignans. Meanwhile, knockdown of AR exerted similar therapeutic effect of Eucommia lignans on DN progression, and AR overexpression reversed the effect of Eucommia lignans. Eucommia lignans alleviated renal injury through the AR/Nrf2/HO-1/AMPK axis. Thus, these findings might provide evidence for the use of Eucommia lignans in treating DN.

Influence of Nitrosyl Iron Complex with Thiosulfate Ligands on Therapeutically Important Targets Related to Type 2 Diabetes Mellitus

The high prevalence of type 2 diabetes mellitus (T2DM), and the lack of effective therapy, determine the need for new treatment options. The present study is focused on the NO-donors drug class as effective antidiabetic agents. Since numerous biological systems are involved in the pathogenesis and progression of T2DM, the most promising approach to the development of effective drugs for the treatment of T2DM is the search for pharmacologically active compounds that are selective for a number of therapeutic targets for T2DM and its complications: oxidative stress, non-enzymatic protein glycation, polyol pathway. The nitrosyl iron complex with thiosulfate ligands was studied in this work. Binuclear iron nitrosyl complexes are synthetic analogues of [2Fe-2S] centers in the regulatory protein natural reservoirs of NO. Due to their ability to release NO without additional activation under physiological conditions, these compounds are of considerable interest for the development of potential drugs. The present study explores the effects of tetranitrosyl iron complex with thiosulfate ligands (TNIC-ThS) on T2DM and its complications regarding therapeutic targets in vitro, as well as its ability to bind liposomal membrane, inhibit lipid peroxidation (LPO), and non-enzymatic glycation of bovine serum albumin (BSA), as well as aldose reductase, the enzyme that catalyzes the reduction in glucose to sorbitol in the polyol pathway. Using the fluorescent probe method, it has been shown that TNIC-ThS molecules interact with both hydrophilic and hydrophobic regions of model membranes. TNIC-ThS inhibits lipid peroxidation, exhibiting antiradical activity due to releasing NO (IC50 = 21.5 ± 3.7 µM). TNIC-ThS was found to show non-competitive inhibition of aldose reductase with Ki value of 5.25 × 10^-4 M. In addition, TNIC-ThS was shown to be an effective inhibitor of the process of non-enzymatic protein glycation in vitro (IC50 = 47.4 ± 7.6 µM). Thus, TNIC-ThS may be considered to contribute significantly to the treatment of T2DM and diabetic complications.

Oxidative Stress in Diabetic Peripheral Neuropathy: Pathway and Mechanism-Based Treatment

Diabetic peripheral neuropathy (DPN) is a major complication of diabetes mellitus with a high incidence. Oxidative stress, which is a crucial pathophysiological pathway of DPN, has attracted much attention. The distortion in the redox balance due to the overproduction of reactive oxygen species (ROS) and the deregulation of antioxidant defense systems promotes oxidative damage in DPN. Therefore, we have focused on the role of oxidative stress in the pathogenesis of DPN and elucidated its interaction with other physiological pathways, such as the glycolytic pathway, polyol pathway, advanced glycosylation end products, protein kinase C pathway, inflammation, and non-coding RNAs. These interactions provide novel therapeutic options targeting oxidative stress for DPN. Furthermore, our review addresses the latest therapeutic strategies targeting oxidative stress for the rehabilitation of DPN. Antioxidant supplements and exercise have been proposed as fundamental therapeutic strategies for diabetic patients through ROS-mediated mechanisms. In addition, several novel drug delivery systems can improve the bioavailability of antioxidants and the efficacy of DPN.

Unearthing of the Antidiabetic Potential of Aqueous Extract of Solanum betaceum Cav. Leaves

Solanum betaceum Cav., commonly known as tamarillo or Brazilian tomato, belongs to the Solanaceae family. Its fruit is used in traditional medicine and food crops due to its health benefits. Despite the numerous studies involving the fruit, there is no scientific knowledge about the tamarillo tree leaves. In this work, the phenolic profile of aqueous extract obtained from S. betaceum leaves was unveiled for the first time. Five hydroxycinnamic phenolic acids were identified and quantified, including 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, chlorogenic acid, caffeic acid and rosmarinic acid. While the extract displayed no effect on α-amylase, the extract inhibited the activity of α-glucosidase (IC₅₀ = 1617 mg/mL), and it was particularly effective for human aldose reductase (IC₅₀ = 0.236 mg/mL): a key enzyme in glucose metabolism. Moreover, the extract exhibited interesting antioxidant properties, such as a potent capacity to intercept the in vitro-generated reactive species O₂^•- (IC₅₀ = 0.119 mg/mL) and ^•NO (IC₅₀ = 0.299 mg/mL), as well as to inhibit the first stages of lipid peroxidation (IC₅₀ = 0.080 mg/mL). This study highlights the biological potential of S. betaceum leaves. The scarcity of research on this natural resource underscores the need for additional studies in order to fully explore its antidiabetic properties and to promote the value of a species currently at risk of extinction.

Combined metabolomics and gut microbiome to investigate the effects and mechanisms of Yuquan Pill on type 2 diabetes in rats

Yuquan Pill (YQP) is a traditional Chinese medicine (TCM) for the treatment of type 2 diabetes (T2DM) in China for many years, and has a beneficial clinical effect. In this study, the antidiabetic mechanism of YQP was investigated for the first time from the perspective of metabolomics and intestinal microbiota. After 28 days of high-fat feeding, rats were injected intraperitoneally with streptozotocin (STZ, 35 mg/kg) followed by a single oral administration of YQP 2.16 g/kg and metformin 200 mg/kg for 5 weeks. The results showed that YQP was effectively improved insulin resistance and alleviated hyperglycemia and hyperlipidemia associated with T2DM. YQP was found to regulate metabolism and gut microbiota in T2DM rats using untargeted metabolomics and gut microbiota integration. Forty-one metabolites and five metabolic pathways were identified, including Ascorbate and aldarate metabolism, Nicotinate and nicotinamide metabolism, Galactose metabolism, Pentose phosphate pathway and Tyrosine metabolism. YQP can regulate T2DM-induced dysbacteriosis by modulating the abundance of Firmicutes, Bacteroidetes, Ruminococcus, Lactobacillus. The restorative effects of YQP in rats with T2DM have been confirmed and provide a scientific basis for the clinical treatment of diabetic patients.

Response of a Human Lens Epithelial Cell Line to Hyperglycemic and Oxidative Stress: The Role of Aldose Reductase

A common feature of different types of diabetes is the high blood glucose levels, which are known to induce a series of metabolic alterations, leading to damaging events in different tissues. Among these alterations, both increased polyol pathway flux and oxidative stress are considered to play relevant roles in the response of different cells. In this work, the effect on a human lens epithelial cell line of stress conditions, consisting of exposure to either high glucose levels or to the lipid peroxidation product 4-hydroxy-2-nonenal, is reported. The occurrence of osmotic imbalance, alterations of glutathione levels, and expression of inflammatory markers was monitored. A common feature of the two stress conditions was the expression of COX-2, which, only in the case of hyperglycemic stress, occurred through NF-κB activation. In our cell model, aldose reductase activity, which is confirmed as the only activity responsible for the osmotic imbalance occurring in hyperglycemic conditions, seemed to have no role in controlling the onset of the inflammatory phenomena. However, it played a relevant role in cellular detoxification against lipid peroxidation products. These results, in confirming the multifactorial nature of the inflammatory phenomena, highlight the dual role of aldose reductase as having both damaging but also protecting activity, depending on stress conditions.

Designed multiple ligands for the treatment of type 2 diabetes mellitus and its complications: Discovery of (5-arylidene-4-oxo-2-thioxothiazolidin-3-yl)alkanoic acids active as novel dual-targeted PTP1B/AKR1B1 inhibitors

Type 2 diabetes mellitus (T2DM) is a serious chronic disease with an alarmingly growing worldwide prevalence. Current treatment of T2DM mainly relies on drug combinations in order to control blood glucose levels and consequently prevent the onset of hyperglycaemia-related complications. The development of multiple-targeted drugs recently emerged as an attractive alternative to drug combinations for the treatment of complex diseases with multifactorial pathogenesis, such as T2DM. Protein tyrosine phosphatase 1B (PTP1B) and aldose reductase (AKR1B1) are two enzymes crucially involved in the development of T2DM and its chronic complications and, therefore, dual inhibitors targeted to both these enzymes could provide novel agents for the treatment of this complex pathological condition. In continuing our search for dual-targeted PTP1B/AKR1B1 inhibitors, we designed new (5-arylidene-4-oxo-2-thioxothiazolidin-3-yl)alkanoic acids. Among them, 3-(4-phenylbutoxy)benzylidene derivatives 6f and 7f, endowed with interesting inhibitory activity against both targets, proved to control specific cellular pathways implicated in the development of T2DM and related complications.

Evidence of Insulin-Sensitizing and Mimetic Activity of the Sesquiterpene Quinone Avarone, a Protein Tyrosine Phosphatase 1B and Aldose Reductase Dual Targeting Agent from the Marine Sponge Dysidea avara

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by impaired glucose homeostasis and serious long-term complications. First-line therapeutic options for T2DM treatment are monodrug therapies, often replaced by multidrug therapies to ensure that non-responding patients maintain target glycemia levels. The use of multitarget drugs instead of mono- or multidrug therapies has been emerging as a main strategy to treat multifactorial diseases, including T2DM. Therefore, modern drug discovery in its early stages aims to identify potential modulators for multiple targets; for this purpose, exploration of the chemical space of natural products represents a powerful tool. Our study demonstrates that avarone, a sesquiterpene quinone obtained from the sponge Dysidea avara, is capable of inhibiting in vitro PTP1B, the main negative regulator of the insulin receptor, while it improves insulin sensitivity, and mitochondria activity in C2C12 cells. We observe that when avarone is administered alone, it acts as an insulin-mimetic agent. In addition, we show that avarone acts as a tight binding inhibitor of aldose reductase (AKR1B1), the enzyme involved in the development of diabetic complications. Overall, avarone could be proposed as a novel natural hit to be developed as a multitarget drug for diabetes and its pathological complications.

A comprehensive review on the antidiabetic attributes of thiazolidine-4-ones: Synthetic strategies and structure-activity relationships

The thiazolidine-4-one scaffold has recently emerged as a potential pharmacophore having clinical significance for medicinal chemists. This heterocyclic ring has been reported to possess a plethora of biological activities, including antidiabetic activity that has inspired researchers to integrate this core with different pharmacophoric fragments to design novel and effective antidiabetic leads. The antidiabetic activity has been observed due to the ability of the thiazolidine-4-one nucleus to interact with different biological targets, including peroxisome proliferator-activated receptor γ, protein tyrosine phosphatase 1B, aldose reductase, α-glucosidase, and α-amylase. The present review discusses the mode of action of thiazolidine-4-ones through these antidiabetic drug targets. This review attempts to summarize and analyze the recent developments with regard to the antidiabetic potential of thiazolidine-4-ones covering different synthetic strategies, structure-activity relationships, and docking studies reported in the literature. The significance of various structural modifications at C-2, N-3, and C-5 of the thiazolidine-4-one ring has also been discussed in this manuscript. This comprehensive compilation will provide an inevitable scope for the design and development of potential antidiabetic drug candidates having a thiazolidine-4-one core.

Synthesis and structure-activity relationship study of aldose reductase inhibiting marine alkaloid lukianol A and its derivatives

Lukianol A (1a) and its six derivatives 1b-1g, in which each hydroxyl groups of 1a was individually modified, were synthesized via the common intermediate 7a, which was obtained by condensation of the styryl carbazate 10 with p-hydroxyphenylpyruvic acid and subsequent [3,3]-sigmatropic rearrangement. The synthesized lukianol derivatives were evaluated for their ability to inhibit human aldose reductase. 4'-O-methyl (1b) and 4'-dehydroxy (1g) derivatives showed the same level of inhibitory activity as 1a (IC50 2.2 µm), indicating that the 4'-OH is irrelevant for the activity. In contrast, methylation of the hydroxyl group at the 4″'-position (1d) resulted in the loss of activity at a concentration of 10 µm, and masking the hydroxyl group at the 4″-position (1e) caused a 9-fold decrease in activity compared with that of 1b, suggesting that the 4″-OH is an essential group, and the 4″'-OH is required for higher activity.

Association of candidate genes (ALR2, RAGE, and VEGF) polymorphisms with diabetic retinopathy in type 2 diabetic patients of Khyber Pakhtunkhwa, Pakistan

AIM

To evaluate the aldose reductase (ALR2, rs759853), receptor for advanced glycation end products (RAGE, rs2070600), and vascular endothelial growth factor (VEGF, rs833061) association with diabetic retinopathy in type 2 diabetic patients of Khyber Pakhtunkhwa population.

METHODS

A case-control study was conducted on a total of 550 subjects consisting of 186 with diabetic retinopathy (DR) having type 2 diabetes, 180 had type 2 diabetes (T2DM), and 184 healthy controls (HC). All the samples were subjected to DNA isolation using salting-out method followed by SNP genotyping through Tetra-ARMS PCR. Chi square and Exact Fischer tests were used for alleles and genotypes distribution. Odd ratio and confidence interval values were found out by online software Medcalc Odd ratio Calculator.

RESULTS

Multiple parameters such as random blood sugar (RBS) (p < 0.001), fasting blood sugar (FBS) (p < 0.001), HbA1c (p < 0.001), total cholesterol (p < 0.001), LDL (p < 0.001), HDL (p < 0.001), BMI (p < 0.001) and hypertension (p = 0.018) exhibited strong association with DR as compared to DM and HC. Our results displayed that the VEGF-rs833061 and RAGE- rs2070600 exhibited significant association (p < 0.05) with an increased DR risk, when compared with T2DM. In contrast, ALR2 didn't display association with DR (p > 0.05) when compared with T2DM, but showed association (p < 0.05) when compared with HC.

CONCLUSION

Statistically significant association was observed in VEGF-rs833061 and RAGE-rs2070600 with DR in type 2 diabetic patients. While, ALR2- rs759853 didn't exhibit significant association with DR. This is the first study to report the association of candidate genes (ALR2, VEGF and RAGE) with DR in type 2 diabetes of Khyber Pakhtunkhwa population. More similar research studies are recommended with larger data sets in other ethnicities both national and international.

Pharmaceutical Food Science: Search for Bio-Functional Molecules Obtained from Natural Resources to Prevent and Ameliorate Lifestyle Diseases

In this review, our resent pharmaceutical food science research for bio-functional molecules obtained from natural resources that contribute to i) suppression of postprandial blood glucose elevation and/or improvement of glucose tolerance and ii) reduction of visceral fat accumulation and improvement of lipid metabolism were summarized. Based on studies using MONOTORI science, salacinol (1), neokotalanol (4), and trans-tiliroside (20) have been approved or notified by the Consumer Affairs Agency in Japan as functional substances in food with health claims, Food for Specified Health Use and Food with Functional Claims.

The Good, the Bad and the New about Uric Acid in Cancer

Simple Summary

The concentration of uric acid in blood is sex-, age- and diet-dependent and is maintained close to its maximal solubility, indicating that it plays some important role. Indeed, it has been demonstrated that, at physiological concentrations, uric acid is a powerful antioxidant and is a scavenger of singlet oxygen and radicals. At high intracellular concentration, uric acid has been demonstrated to act as a pro-oxidant molecule. Recently, uric acid has been reported to affect the properties of several proteins involved in metabolic regulation and signaling, and the relationship between uric acid and cancer has been extensively investigated. In this review, we present the most recent results on the positive and negative effects played by uric acid in cancer and some new findings and hypotheses about the implication of this metabolite in the pathogenesis of several diseases such as metabolic syndrome, diabetes, and inflammation, thus favoring the development of cancer.

Abstract

Uric acid is the final product of purine catabolism in man and apes. The serum concentration of uric acid is sex-, age- and diet-dependent and is maintained close to its maximal solubility, indicating that it plays some important role. Indeed, it has been demonstrated that, at physiological concentrations, uric acid is a powerful antioxidant, while at high intracellular concentrations, it is a pro-oxidant molecule. In this review, we describe the possible causes of uric acid accumulation or depletion and some of the metabolic and regulatory pathways it may impact. Particular attention has been given to fructose, which, because of the complex correlation between carbohydrate and nucleotide metabolism, causes uric acid accumulation. We also present recent results on the positive and negative effects played by uric acid in cancer and some new findings and hypotheses about the implication of this metabolite in a variety of signaling pathways, which can play a role in the pathogenesis of diseases such as metabolic syndrome, diabetes, and inflammation, thus favoring the development of cancer. The loss of uricase in Homo sapiens and great apes, although exposing these species to the potentially adverse effects of uric acid, appears to be associated with evolutionary advantages.

Stimuli-responsive therapeutic systems for the treatment of diabetic infected wounds

Diabetic wound infection is a common disease that has significantly reduced people's quality of life. Although tremendous achievements have been made in clinical treatment, the crucial challenge in diabetic infected wound management stems from the detrimental diabetic wound environment and the emergence of bacterial resistance after long-term medication, which result in a reduced efficacy, an increased dosage of medication, and severe side effects. To tackle these issues, it is of great significance to develop an innovative treatment strategy for diabetic wound infection therapy. Currently, the exploitation of nanobiomaterial-based therapeutic systems for diabetic infected wounds is booming, and therapeutic systems with a stimuli-responsive performance have received extensive attention. These therapeutic systems are able to accelerate diabetic infected wound healing due to the on-demand release of therapeutic agents in diabetic infected wounds in response to stimulating factors. Based on the characteristics of diabetic infected wounds, many endogenous stimuli-responsive (e.g., glucose, enzyme, hypoxia, and acidity) therapeutic systems have been employed for the targeted treatment of infected wounds in diabetic patients. Additionally, exogenous stimulants, including light, magnetism, and temperature, are also capable of achieving on-demand drug release and activation. In this review, the characteristics of diabetic infected wounds are presented, and then exogenous/endogenous stimuli therapeutic systems for the treatment of diabetic infected wounds are summarized. Finally, the current challenges and future outlook of stimuli-responsive therapeutic systems are also discussed.

Dissecting the Activity of Catechins as Incomplete Aldose Reductase Differential Inhibitors through Kinetic and Computational Approaches

Simple Summary

The increased glucose levels occurring in diabetes lead to several metabolic alterations responsible for the onset of the so-called diabetic complications, which include nephropathies, neuropathies, retinopathies, and cataract. An increased flux of glucose through the polyol pathway is considered the most relevant among these alterations. For this reason, the block of the polyol pathway, through the inhibition of the enzyme aldose reductase, is considered a valuable strategy to impair the onset of diabetic complications. However, aldose reductase also exerts a beneficial effect inside cells, since it can remove toxic aldehydes. Thus, to ameliorate the outcome of the use of aldose reductase inhibitors, the use of “differential inhibitors” has been proposed. These inhibitors should block the catalytic activity depending on the substrate the enzyme is working on, thus preserving the detoxifying action of the enzyme. In this work, derivatives of catechins are analyzed to evaluate their inhibitory action on aldose reductase. The study was conducted both in vitro on the isolated enzyme and in silico through a computational approach. Results demonstrated that gallocatechin gallate and catechin gallate act as differential inhibitors and that this action may be linked to an incomplete inhibitory effect.

Abstract

The inhibition of aldose reductase is considered as a strategy to counteract the onset of both diabetic complications, upon the block of glucose conversion in the polyol pathway, and inflammation, upon the block of 3-glutathionyl-4-hydroxynonenal reduction. To ameliorate the outcome of aldose reductase inhibition, minimizing the interference with the detoxifying role of the enzyme when acting on toxic aldehydes, “differential inhibitors”, i.e., molecules able to inhibit the enzyme depending on the substrate the enzyme is working on, has been proposed. Here we report the characterization of different catechin derivatives as aldose reductase differential inhibitors. The study, conducted through both a kinetic and a computational approach, highlights structural constraints of catechin derivatives relevant in order to affect aldose reductase activity. Gallocatechin gallate and catechin gallate emerged as differential inhibitors of aldose reductase able to preferentially affect aldoses and 3-glutathionyl-4-hydroxynonenal reduction with respect to 4-hydroxynonenal reduction. Moreover, the results highlight how, in the case of aldose reductase, a substrate may affect not only the model of action of an inhibitor, but also the degree of incompleteness of the inhibitory action, thus contributing to differential inhibitory phenomena.

Moving toward a new horizon for the aldose reductase inhibitor epalrestat to treat drug-resistant cancer

Epalrestat (EPA) is a potent inhibitor of aldose reductases AKR1B1 and AKR1B10, used for decades in Japan for the treatment of diabetic peripheral neuropathy. This orally-active, brain-permeable small molecule, with a relatively rare and essential 2-thioxo-4-thiazolidinone motif, functions as a regulator intracellular carbonyl species. The repurposing of EPA for the treatment of pediatric rare diseases, brain disorders and cancer has been proposed. A detailed analysis of the mechanism of action, and the benefit of EPA to combat advanced malignancies is offered here. EPA has revealed marked anticancer activities, alone and in combination with cytotoxic chemotherapy and targeted therapeutics, in experimental models of liver, colon, and breast cancers. Through inhibition of AKR1B1 and/or AKR1B10 and blockade of the epithelial-mesenchymal transition, EPA largely enhances the sensitivity of cancer cells to drugs like doxorubicin and sorafenib. EPA has revealed a major anticancer effect in an experimental model of basal-like breast cancer and clinical trials have been developed in patients with triple-negative breast cancer. The repurposing of the drug to treat chemo-resistant solid tumors seems promising, but more studies are needed to define the best trajectory for the positioning of EPA in oncology.

An update on nutritional profile, phytochemical compounds, health benefits, and potential applications in the food industry of pulses seed coats: A comprehensive review

Pulses, as a sustainable source of nutrients, are an important choice for human diets, but vast quantities of seed coats generated in pulses processing are usually discarded or used as low-value ruminant feed. It has been demonstrated that pulses seed coats are excellent sources of dietary nutrients and phytochemicals with potential health benefits. With growing interest in the sustainable use of resources and the circular economy, utilization of pulses seed coats to recover these valuable components is a core objective for their valorization and an important step toward agricultural sustainability. This review comprehensively provides a comprehensive insight on the nutritional and phytochemical profiles presented in pulses seed coats and their health benefits obtained from the findings of in vitro and in vivo studies. Furthermore, in the food industry, pulses seed coats can be acted as potential food ingredients with nutritional, antioxidant and antimicrobial characteristics or as the matrix or active components of films for food packaging and edible coatings. A better understanding of pulses seed coats may provide a reference for increasing the overall added value and realizing the pulses' sustainable diets.

Scutellarin acts on the AR-NOX axis to remediate oxidative stress injury in a mouse model of cerebral ischemia/reperfusion injury

BACKGROUND

Oxidative stress plays an important role in the pathology of ischemic stroke. Studies have confirmedthat scutellarin has antioxidant effects against ischemic injury, and we also reported that the involvement of Aldose reductase (AR) in oxidative stress and cerebral ischemic injury, in this study we furtherly explicit whether the antioxidant effect of scutellarin on cerebral ischemia injury is related to AR gene regulation and its specific mechanism.

METHODS

C57BL/6N mice (Wild-type, WT) and AR knockout (AR^-/-) mice suffered from transient middle cerebral artery occlusion (tMCAO) injury (1 h occlusion followed by 3 days reperfusion), and scutellarin was administered from 2 h before surgery to 3 days after surgery. Subsequently, neurological function was assessed by the modified Longa score method, the histopathological morphology observed with 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (HE) staining. Enzyme-linked immunosorbent assay (Elisa) was used to detect the levels of ROS, 4-hydroxynonenal (4-HNE), 8-hydroxydeoxyguanosine (8-OHDG), Neurotrophin-3 (NT-3), poly ADP-ribose polymerase-1 (PARP1) and 3-nitrotyrosine (3-NT) in the ischemic penumbra regions. Quantitative proteomics profiling using quantitative nano-HPLC-MS/MS were performed to compare the protein expression difference between AR^-/- and WT mice with or without tMCAO injury. The expression of AR, nicotinamide adenine dinucleotide phosphate oxidases (NOX1, NOX2 and NOX4) in the ipsilateral side of ischemic brain were detected by qRT-PCR, Western blot and immunofluorescence co-staining with NeuN.

RESULTS

Scutellarin treatment alleviated brain damage in tMCAO stroke model such as improved neurological function deficit, brain infarct area and neuronal injury and reduced the expression of oxidation-related products, moreover, also down-regulated tMCAO induced AR mRNA and protein expression. In addition, the therapeutic effect of scutellarin on the reduction of cerebral infarction area and neurological function deficits abolished in AR^-/- mice under ischemia cerebral injury, which indicated that the effect of scutellarin treatment on tMCAO injury is through regulating AR gene. Proteomic analysis of AR^-/- and WT mice indicated AR knockout would affect oxidation reaction even as NADPH related process and activity in mice under cerebral ischemia conditions. Moreover, NOX isoforms (NOX1, NOX2 and NOX4) mRNA and protein expression were significant decreased in neurons of penumbra region in AR^-/- mice compared with that in WT mice at 3d after tMCAO injury, which indicated that AR should be the upstream protein regulating NOX after cerebral ischemia.

CONCLUSIONS

We first reported that AR directly regulates NOX subtypes (not only NOX2 but also NOX1 and NOX4) after cerebral ischaemic injury. Scutellarin specifically targets the AR-NOX axis and has antioxidant effects in mice with cerebral ischaemic injury, providing a theoretical basis and accurate molecular targets for the clinical application of scutellarin.

Inulin-type fructans change the gut microbiota and prevent the development of diabetic nephropathy

Diabetic nephropathy (DN) is the most common cause of end-stage renal disease, and few treatment options that prevent the progressive loss of renal function are available. Studies have shown that dietary fiber intake improves kidney diseases and metabolism-related diseases, most likely through short-chain fatty acids (SCFAs). The present study aimed to examine the protective effects of inulin-type fructans (ITFs) on DN through 16 S rRNA gene sequencing, gas chromatographymass spectrometry (GCMS) analysis and fecal microbiota transplantation (FMT). The results showed that ITFs supplementation protected against kidney damage in db/db mice and regulated the composition of the gut microbiota. Antibiotic treatment and FMT experiments further demonstrated a key role of the gut microbiota in mediating the beneficial effects of ITFs. The ITFs treatment-induced changes in the gut microbiota led to an enrichment of SCFA-producing bacteria, especially the genera Akkermansia and Candidatus Saccharimonas, which increased the fecal and serum acetate concentrations. Subsequently, acetate supplementation improved glomerular damage and renal fibrosis by attenuating mitochondrial dysfunction and reducing toxic glucose metabolite levels. In conclusion, ITFs play a renoprotective role by modulating the gut microbiota and increasing acetate production. Furthermore, acetate mediates renal protection by regulating glucose metabolism, decreasing glycotoxic product levels and improving mitochondrial function.

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.

Models of enzyme inhibition and apparent dissociation constants from kinetic analysis to study the differential inhibition of aldose reductase

In order to explain the negative slope of KappM/kappcat versus inhibitor concentration observed in the study of epigallocatechin gallate acting as an inhibitor of aldose reductase, a kinetic analysis was performed to rationalise the phenomenon. Classical and non-classical models of complete and incomplete enzyme inhibition were devised and analysed to obtain rate equations suitable for the interpretation of experimental data. The results obtained from the different approaches were discussed in terms of the meaning of the emerging kinetic constants. A decrease of KappM/kappcat versus the inhibitor concentration was revealed to be a valuable indication of the occurrence of an incomplete inhibition. This indication, which is univocal in the case of an uncompetitive inhibition, may be especially useful when the residual activity resulting from inhibition is rather low.