Myricetin inhibits advanced glycation end product (AGE)-induced migration of retinal pericytes through phosphorylation of ERK1/2, FAK-1, and paxillin in vitro and in vivo

In situ Forming Nanoemulgel for Diabetic Retinopathy: Development, characterization, and in vitro efficacy assessment

Diabetic retinopathy, the most common microvascular complication of diabetes mellitus, is the leading cause of vision impairment worldwide. Flavonoids with antioxidant properties have been shown to slow its progression. Myricetin, a flavonoid polyphenolic compound, possesses antioxidant properties, but its clinical use in ocular delivery is limited by poor aqueous solubility, stability, and bioavailability. Recently, in situ gels have gained interest as ocular drug delivery vehicles due to their ease of installation and sustained drug release. This study aimed to develop a myricetin-loaded thermoresponsive in situ nanoemulgel to enhance its efficacy in treating diabetic retinopathy. Nanoemulsions were developed via aqueous phase titration using Sefsol 218 as the oil phase, Kolliphore RH40 as the surfactant, and PEG 400 as the co-surfactant. Physicochemical evaluations identified formulation batch ISG17, consisting of 10% oil phase, 30% Smix (1:2), and 60% distilled water, as the optimal formulation. The developed in situ nanoemulgel showed significant enhancement in corneal permeation and retention, which was further confirmed by fluorescence microscopy. Ocular tolerability was demonstrated through corneal hydration tests and histopathology investigations. The antioxidant potential of the myricetin-loaded nanoemulgel was assessed using the DPPH assay. Myricetin was found to be an efficient antioxidant, as indicated by its IC50 values compared to ascorbic acid. The MTT cell viability assay results showed that the developed formulation effectively inhibits the proliferation of Y79 retinoblastoma cells, demonstrating comparable efficacy to the standard marketed preparation Avastin (Bevacizumab injection). In conclusion, the nanoemulsion formulation containing a thermoresponsive polymer for in situ gelling presents a promising drug delivery system, offering superior therapeutic efficacy and better patient compliance for the treatment of diabetic retinopathy.

Myricetin induces M2 macrophage polarization to alleviate renal tubulointerstitial fibrosis in diabetic nephropathy via PI3K/Akt pathway

BACKGROUND

Development of end-stage renal disease is predominantly attributed to diabetic nephropathy (DN). Previous studies have indicated that myricetin possesses the potential to mitigate the pathological alterations observed in renal tissue. Nevertheless, the precise molecular mechanism through which myricetin influences the progression of DN remains uncertain.

AIM

To investigate the effects of myricetin on DN and explore its potential therapeutic mechanism.

METHODS

Db/db mice were administered myricetin intragastrically on a daily basis at doses of 50 mg/kg or 100 mg/kg for a duration of 12 wk. Subsequently, blood and urine indexes were assessed, along with examination of renal tissue pathology. Kidney morphology and fibrosis were evaluated using various staining techniques including hematoxylin and eosin, periodic acid-Schiff, Masson's trichrome, and Sirius-red. Additionally, high-glucose culturing was conducted on the RAW 264.7 cell line, treated with 25 mM myricetin or co-administered with the PI3K/Akt inhibitor LY294002 for a period of 24 h. In both in vivo and in vitro settings, quantification of inflammation factor levels was conducted using western blotting, real-time qPCR and ELISA.

RESULTS

In db/db mice, administration of myricetin led to a mitigating effect on DN-induced renal dysfunction and fibrosis. Notably, we observed a significant reduction in expressions of the kidney injury markers kidney injury molecule-1 and neutrophil gelatinase associated lipocalin, along with a decrease in expressions of inflammatory cytokine-related factors. Furthermore, myricetin treatment effectively inhibited the up-regulation of tumor necrosis factor-alpha, interleukin-6, and interluekin-1β induced by high glucose in RAW 264.7 cells. Additionally, myricetin modulated the M1-type polarization of the RAW 264.7 cells. Molecular docking and bioinformatic analyses revealed Akt as the target of myricetin. The protective effect of myricetin was nullified upon blocking the polarization of RAW 264.7 via inhibition of PI3K/Akt activation using LY294002.

CONCLUSION

This study demonstrated that myricetin effectively mitigates kidney injury in DN mice through the regulation of macrophage polarization via the PI3K/Akt signaling pathway.

Role of polyphenols in the management of diabetic complications

BACKGROUND

Diabetes Mellitus is an endocrine disorder that will affect, about 693 million adults by 2045 worldwide, (>50% increase from 2017). The conventional treatment of the disease, include the oral hypoglycemic drugs which are given in combination with other drugs and are known to possess various adverse effects like gastrointestinal disturbance, nausea, water retention etc. PURPOSE: Due to the urgent need of combating this disorder without side effects, the alternative and complementary therapies should be explored due to their natural origins and comparable safety. Herbal sources serve as new leads, due to the presence of phytoconstituents with potential therapeutic properties, efficacy and safety. In this review, we tried to summarise the polyphenolic phytoconstituents effective in the treatment of diabetic complications.

METHODS

A systematic literature search was conducted using 4 databases (Google scholar, Pubmed, Scopus, Embase) for the identification of relevant data. Search was performed using various key words such as "diabetes", "polyphenols", "marine sources","anti-diabetic polyphenols". The in vitro studies involving the cell lines used in diabetes and animal models were also considered for inclusion. Additional research papers were identified by reviewing abstracts, scrutinizing reference lists, and reviewing previously published review articles.

RESULTS

Polyphenols, a group of phytoconstituents are known worldwide for their tremendous antioxidant potential. So, various research groups have explored their mechanism and therapeutic value in diabetic complications, to improve the insulin sensitivity and glucose metabolism, in controlling the glycemic conditions.

CONCLUSION

Polyphenols exhibit effective therapeutic potential in managing diabetic complications through their multifaceted mechanism of action. They exhibit antioxidative, anti-inflammatory, and anti-glycemic properties, which collectively contribute to their beneficial effects in mitigating diabetic complications. Thus, the inclusion of polyphenols into the diet, may be cosidered as an approach of managing diabetes on long term basis. In this review, we have tried to identify polyphenols effective in diabetes and summarize their mechanism of action along with their potential, for the treatment of diabetic complications.

Retinal Neurodegeneration in Euglycemic Hyperinsulinemia, Prediabetes, and Diabetes

Diabetic retinopathy (DR) is a challenging public health problem mainly because of its growing prevalence and risk of blindness. In general, our current knowledge and practice have failed to prevent the onset or progression of DR to sight-threatening complications. While there are treatment options for sight-threatening complications of DR, it is crucial to pay more attention to the early stages of DR to decrease its prevalence. Growing evidence suggests many pathologic changes occur before clinical presentations of DR in euglycemic hyperinsulinemia, prediabetes, and diabetes. These pathological changes occur in retinal neurons, glia, and microvasculature. A new focus on these preclinical pathologies - especially on hyperinsulinemia - may provide further insight into disease mechanisms, endpoints for clinical trials, and druggable targets in early disease. Here, we review the current evidence on the pathophysiological changes reported in preclinical DR and appraise preventive and treatment options for DR.

Aspalathin and Other Rooibos Flavonoids Trapped α-Dicarbonyls and Inhibited Formation of Advanced Glycation End Products In Vitro

The excessive dietary intake of simple sugars and abnormal metabolism in certain diseases contribute to the increased production of α-dicarbonyls (α-DCs), such as methylglyoxal (MGO) and glyoxal (GO), the main precursors of the formation of advanced glycation end products (AGEs). AGEs play a vital role, for example, in the development of cardiovascular diseases and diabetes. Aspalathus linearis (Burman f.) R. Dahlgren (known as rooibos tea) exhibits a wide range of activities beneficial for cardio-metabolic health. Thus, the present study aims to investigate unfermented and fermented rooibos extracts and their constituents for the ability to trap MGO and GO. The individual compounds identified in extracts were tested for the capability to inhibit AGEs (with MGO or GO as a glycation agent). Ultra-high-performance liquid chromatography coupled with an electrospray ionization mass spectrometer (UHPLC-ESI-MS) was used to investigate α-DCs' trapping capacities. To evaluate the antiglycation activity, fluorescence measurement was used. The extract from the unfermented rooibos showed a higher ability to capture MGO/GO and inhibit AGE formation than did the extract from fermented rooibos, and this effect was attributed to a higher content of dihydrochalcones. The compounds detected in the extracts, such as aspalathin, nothofagin, vitexin, isovitexin, and eriodictyol, as well as structurally related phloretin and phloroglucinol (formed by the biotransformation of certain flavonoids), trapped MGO, and some also trapped GO. AGE formation was inhibited the most by isovitexin. However, it was the high content of aspalathin and its higher efficiency than that of metformin that determined the antiglycation and trapping properties of green rooibos. Therefore, A. linearis, in addition to other health benefits, could potentially be used as an α-DC trapping agent and AGE inhibitor.

Unconventional avenues to decelerated diabetic retinopathy

Diabetic retinopathy (DR) is an important microvascular complication of diabetes mellitus (DM), causing significant visual impairment worldwide. Current gold standards for retarding the progress of DR include blood sugar control and regular fundus screening. Despite these measures, the incidence and prevalence of DR and vision-threatening DR remain high. Given its slowly progressive course and long latent period, opportunities to contain or slow DR before it threatens vision must be explored. This narrative review assesses the recently described unconventional strategies to retard DR progression. These include gut-ocular flow, gene therapy, mitochondrial dysfunction-oxidative stress, stem cell therapeutics, neurodegeneration, anti-inflammatory treatments, lifestyle modification, and usage of phytochemicals. These therapies impact DR directly, while some of them also influence DM control. Most of these strategies are currently in the preclinical stage, and clinical evidence remains low. Nevertheless, our review suggests that these approaches have the potential for human use to prevent the progression of DR.

Spinach Methanolic Extract Attenuates the Retinal Degeneration in Diabetic Rats

It has been suggested that spinach methanolic extract (SME) inhibits the formation of advanced glycation end products (AGEs), which are increased during diabetes progression, so it is important to know if SME has beneficial effects in the diabetic retina. In this study, in vitro assays showed that SME inhibits glycation, carbonyl groups formation, and reduced-thiol groups depletion in bovine serum albumin incubated either reducing sugars or methylglyoxal. The SME effect in retinas of streptozotocin-induced diabetic rats (STZ) was also studied (n = 10) in the normoglycemic group, STZ, STZ rats treated with SME, and STZ rats treated with aminoguanidine (anti-AGEs reference group) during 12 weeks. The retina was sectioned and immunostained for Nε-carboxymethyl lysine (CML), receptor RAGE, NADPH-Nox4, inducible nitric oxide synthase (iNOS), 3-nitrotyrosine (NT), nuclear NF-κB, vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), S100B protein, and TUNEL assay. Lipid peroxidation was determined in the whole retina by malondialdehyde (MDA) levels. The results showed that in the diabetic retina, SME reduced the CML-RAGE co-localization, oxidative stress (NOX4, iNOS, NT, MDA), inflammation (NF-κB, VEGF, S100B, GFAP), and apoptosis (p < 0.05). Therefore, SME could attenuate the retinal degeneration by inhibition of CML-RAGE interaction.

The Benefits of Flavonoids in Diabetic Retinopathy

Diabetic retinopathy (DR), one of the most common complications of diabetes, is the leading cause of legal blindness among adults of working age in developed countries. After 20 years of diabetes, almost all patients suffering from type I diabetes mellitus and about 60% of type II diabetics have DR. Several studies have tried to identify drugs and therapies to treat DR though little attention has been given to flavonoids, one type of polyphenols, which can be found in high levels mainly in fruits and vegetables, but also in other foods such as grains, cocoa, green tea or even in red wine. Flavonoids have anti-inflammatory, antioxidant and antiviral effects. Since it is known that diabetes induces oxidative stress and inflammation in the retina leading to neuronal death in the early stages of the disease, the use of these compounds can prove to be beneficial in the prevention or treatment of DR. In this review, we summarize the molecular and cellular effects of flavonoids in the diabetic retina.

The Protective Effects of Myricetin against Cardiovascular Disease

Cardiovascular disease (CVD) is the leading cause of death globally, except Africa, and poses a severe health burden worldwide. Both in vitro and in vivo studies have demonstrated the protective effects of myricetin for preventing CVD. For this review, we have assessed the literature from 2009 to 2019 at home and abroad to uncover the protective roles of myricetin for preventing CVD. Myricetin exhibits cardioprotective, anti-hypertensive, anti-atherosclerotic, anti-hyperglycemic, and anti-hyperlipidemic effects. In addition, myricetin may alleviate some of the complications caused by adult-onset diabetes. The combined functions of myricetin allow for the prevention of CVD. This review describes the possible therapeutic benefits of myricetin, along with its potential mechanisms of action, to support the clinical use of the myricetin for the prevention of CVD.

Ethnoveterinary plants of Pakistan: a review

BACKGROUND

Ethnoveterinary medicine is crucial in many rural areas of the world since people living in remote and marginal areas rely significantly on traditional herbal therapies to treat their domestic animals. In Pakistan, communities residing in remote areas, and especially those still attached to pastoralist traditions, have considerable ethnoveterinary herbal knowledge and they sometimes use this knowledge for treating their animals. The main aim of the study was to review the literature about ethnoveterinary herbals being used in Pakistan in order to articulate potential applications in modern veterinary medicine. Moreover, the review aimed to analyze possible cross-cultural and cross regional differences.

METHODS

We considered the ethnobotanical data of Pakistan published in different scientific journals from 2004 to 2018. A total of 35 studies were found on ethnoveterinary herbal medicines in the country. Due to the low number of field studies, we considered all peer-reviewed articles on ethnoveterinary herbal practices in the current review. All the ethnobotanical information included in these studies derived from interviews which were conducted with shepherds/animals breeders as well as healers.

RESULTS

Data from the reviewed studies showed that 474 plant species corresponding to 2386 remedies have been used for treating domestic animals in Pakistan. The majority of these plants belong to Poaceae (41 species) followed by the Asteraceae (32 species) and Fabaceae (29 species) botanical families, thus indicating a possible prevalence of horticultural-driven gathering patterns. Digestive problems were the most commonly treated diseases (25%; 606 remedies used), revealing the preference that locals have for treating mainly minor animal ailments with herbs. The least known veterinary plants recorded in Pakistan were Abutilon theophrasti, Agrostis gigantea, Allardia tomentosa, Aristida adscensionis, Bothriochloa bladhii, Buddleja asiatica, Cocculus hirsutus, Cochlospermum religiosum, Cynanchum viminale, Dactylis glomerata, Debregeasia saeneb, Dichanthium annulatum, Dracocephalum nuristanicum, Flueggea leucopyrus, Launaea nudicaulis, Litsea monopetala, Sibbaldianthe bifurca, Spiraea altaica, and Thalictrum foetidum. More importantly, cross-cultural comparative analysis of Pathan and non-Pathan ethnic communities showed that 28% of the veterinary plants were mentioned by both communities. Cross-regional comparison demonstrated that only 10% of the plant species were used in both mountain and plain areas. Reviewed data confirm therefore that both ecological and cultural factors play a crucial role in shaping traditional plant uses.

CONCLUSION

The herbal ethnoveterinary heritage of Pakistan is remarkable, possibly because of the pastoral origins of most of its peoples. The integration of the analyzed complex bio-cultural heritage into daily veterinary practices should be urgently fostered by governmental and non-governmental institutions dealing with rural development policies in order to promote the use of local biodiversity for improving animal well-being and possibly the quality of animal food products as well.

The receptor for advanced glycation end-products enhances lung epithelial wound repair: An in vitro study

Re-epithelialization of the alveolar surface is a key process of lung alveolar epithelial barrier repair after acute lung injury. The receptor for advanced glycation end-products (RAGE) pathway plays key roles in lung homeostasis, and its involvement in wound repair has been already reported in human bronchial epithelial cells. However, its effects on lung alveolar epithelial repair after injury remain unknown. We investigated whether RAGE stimulation with its ligands high-mobility group box 1 protein (HMGB1) or advanced glycation end-products (AGEs), alone or associated with RAGE inhibition using RAGE antagonist peptide, affects in vitro wound healing in human alveolar epithelial A549 cells. We further asked whether these effects could be associated with changes in cell proliferation and migration. We found that treatment of A549 cells with HMGB1 or AGEs promotes RAGE-dependent wound healing after a scratch assay. In addition, both RAGE ligands increased cell proliferation in a RAGE-dependent manner. Treatment with HMGB1 increased migration of alveolar epithelial cells at 12 h, independently of RAGE, whereas AGEs stimulated migration as measured 48 h after injury in a RAGE-dependent manner. Taken together, these results suggest that RAGE pathway is involved in lung alveolar epithelial wound repair, possibly through enhanced cell migration and proliferation.

Inhibition of Sema4D/PlexinB1 signaling alleviates vascular dysfunction in diabetic retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes and leads to blindness. Anti‐VEGF is a primary treatment for DR. Its therapeutic effect is limited in non‐ or poor responders despite frequent injections. By performing a comprehensive analysis of the semaphorins family, we identified the increased expression of Sema4D during oxygen‐induced retinopathy (OIR) and streptozotocin (STZ)‐induced retinopathy. The levels of soluble Sema4D (sSema4D) were significantly increased in the aqueous fluid of DR patients and correlated negatively with the success of anti‐VEGF therapy during clinical follow‐up. We found that Sema4D/PlexinB1 induced endothelial cell dysfunction via mDIA1, which was mediated through Src‐dependent VE‐cadherin dysfunction. Furthermore, genetic disruption of Sema4D/PlexinB1 or intravitreal injection of anti‐Sema4D antibody reduced pericyte loss and vascular leakage in STZ model as well as alleviated neovascularization in OIR model. Moreover, anti‐Sema4D had a therapeutic advantage over anti‐VEGF on pericyte dysfunction. Anti‐Sema4D and anti‐VEGF also conferred a synergistic therapeutic effect in two DR models. Thus, this study indicates an alternative therapeutic strategy with anti‐Sema4D to complement or improve the current treatment of DR.

Role of Moesin Phosphorylation in Retinal Pericyte Migration and Detachment Induced by Advanced Glycation Endproducts

Proliferative diabetic retinopathy (PDR) involves persistent, uncontrolled formation of premature blood vessels with reduced number of pericytes. Our previous work showed that advanced glycation endproducts (AGEs) induced angiogenesis in human umbilical vein endothelial cells, mouse retina, and aortic ring, which was associated with moesin phosphorylation. Here we investigated whether moesin phosphorylation may contribute to pericyte detachment and the development of PDR. Primary retinal microvascular pericytes (RMPs) were isolated, purified from weanling rats, and identified by cellular markers α-SMA, PDGFR-β, NG2, and desmin using immunofluorescence microscopy. Effects of AGE-BSA on proliferation and migration of RMPs were examined using CCK-8, wound healing, and transwell assays. Effects on moesin phosphorylation were examined using western blotting. The RMP response to AGE-BSA was also examined when cells expressed the non-phosphorylatable Thr558Ala mutant or phospho-mimicking Thr558Asp mutant of moesin or were treated with ROCK inhibitor Y27632. Colocalization and interaction between CD44, phospho-moesin, and F-actin were observed. Experiments with cultured primary RMPs showed that AGE-BSA inhibited the proliferation, enhanced the migration, and increased moesin phosphorylation in a dose- and time-dependent manner. AGE-BSA also triggered the rearrangement of F-actin and promoted the interaction of CD44 with phospho-moesin in RMPs. These effects were abrogated in cells expressing the non-phosphorylatable moesin mutant and the application of ROCK inhibitor Y27632 attenuated AGE-induced alteration in cultured RMPs by abolishing the phosphorylation of moesin. However, those AGE-induced pathological process occurred in RMPs expressed the phospho-mimicking moesin without AGE-BSA treatment. It is concluded that AGEs could activate ROCK to mediate moesin phosphorylation at Thr558, and resulting phospho-moesin interacts with CD44 to form CD44 cluster, which might stimulate the migration of RMPs and subsequent RMP detachment in microvessel. This pathway may provide new drug targets against immature neovessel formation in PDR.

Specific Inhibition of CYP4A Alleviates Myocardial Oxidative Stress and Apoptosis Induced by Advanced Glycation End-Products

High exposure to advanced glycation end-products (AGEs) may induce cardiotoxicity. However, the effects and mechanisms remain to be further clarified. CYP4A plays an important role in the pathophysiological process of myocardial abnormalities by modulating oxidative stress and apoptosis (OS/Apop) signaling pathway. The present work aimed to investigate whether CYP4A mediates AGEs-induced myocardial injury. AGEs solution was administered intragastrically to C57BL/6 mice for 60 days, while the specific inhibitor of CYP4A, HET0016, was given from the 47th day via intraperitoneal injection for 2 weeks. Levels of OS/Apop in heart tissue were measured. The effects on the cell viability and apoptosis were detected in primary rat cardiomyocytes. To further investigate the mechanism, H9c2 cells were treated with HET0016 or small interfering RNAs (siRNAs) against CYP4a mRNA before incubation with AGEs. Exposure to AGEs led to significantly increased expression of CYP4A and levels of OS/Apop in heart and H9c2 cells both in vivo and in vitro. The OS/Apop pathway was activated with increased expression of NOX2, p-JNK, and cleaved caspase-3 (c-caspase-3) and decreased expression of p-Akt and Bcl-xL both in vivo and in vitro. Specific CYP4A suppression by HET0016 or siRNA exerted significant protective effects by attenuating AGEs-induced OS/Apop pathways in vitro. Our results demonstrate that specific inhibition of CYP4A might be a potential therapeutic option for myocardial injury induced by AGEs.

Fluorofenidone affects hepatic stellate cell activation in hepatic fibrosis by targeting the TGF-β1/Smad and MAPK signaling pathways

The aim of the present research was to study the therapeutic impacts of fluorofenidone (AKF-PD) on pig serum (PS)-induced liver fibrosis in rats and the complex molecular mechanisms of its effects on hepatic stellate cells (HSCs). Wistar rats were randomly divided into normal control, PS and PS/AKF-PD treatment groups. The activated human HSC LX-2 cell line was also treated with AKF-PD. The expression of collagen I and III, and α-smooth muscle actin (α-SMA) was determined by immunohistochemical staining and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blotting and/or RT-qPCR analyses were used to determine the expression of transforming growth factor (TGF)-β1, α-SMA, collagen I, mothers against decapentaplegic homolog (Smad)-3, extracellular signal-regulated kinase (ERK)1/2, p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK). AKF-PD attenuated the degree of hepatic fibrosis and liver injury in vivo, which was associated with the downregulation of collagen I and III, and α-SMA at the mRNA and protein levels. In vitro, AKF-PD treatment significantly reduced the TGF-β1-induced activation of HSCs, as determined by the reduction in collagen I and α-SMA protein expression. The TGF-β1-induced upregulation of the phosphorylation of Smad 3, ERK1/2, p38 and JNK was attenuated by AKF-PD treatment. These findings suggested that AKF-PD attenuated the progression of hepatic fibrosis by suppressing HSCs activation via the TGF-β1/Smad and MAPK signaling pathways, and therefore that AKF-PD may be suitable for use as a novel therapeutic agent against liver fibrosis.

Targeting pericytes for neurovascular regeneration

Pericytes, as a key cellular part of the blood-brain barrier, play an important role in the maintenance of brain neurovascular unit. These cells participate in brain homeostasis by regulating vascular development and integrity mainly through secreting various factors. Pericytes per se show different restorative properties after blood-brain barrier injury. Upon the occurrence of brain acute and chronic diseases, pericytes provoke immune cells to regulate neuro-inflammatory conditions. Loss of pericytes in distinct neurologic disorders intensifies blood-brain barrier permeability and leads to vascular dementia. The therapeutic potential of pericytes is originated from the unique morphological shape, location, and their ability in providing vast paracrine and juxtacrine interactions. A subset of pericytes possesses multipotentiality and exhibit trans-differentiation capacity in the context of damaged tissue. This review article aimed to highlight the critical role of pericytes in restoration of the blood-brain barrier after injury by focusing on the dynamics of pericytes and cross-talk with other cell types.

Dietary Chrysin Suppresses Formation of Actin Cytoskeleton and Focal Adhesion in AGE-Exposed Mesangial Cells and Diabetic Kidney: Role of Autophagy

Advanced glycation end products (AGE) play a causative role in the development of aberrant phenotypes of intraglomerular mesangial cells, contributing to acute/chronic glomerulonephritis. The aim of this study was to explore mechanistic effects of the flavonoid chrysin present in bee propolis and herbs on actin dynamics, focal adhesion, and the migration of AGE-exposed mesangial cells. The in vitro study cultured human mesangial cells exposed to 33 mM glucose and 100 μg/mL AGE-bovine serum albumin (AGE-BSA) for up to 5 days in the absence and presence of 1⁻20 μM chrysin. The in vivo study employed db/db mice orally administrated for 10 weeks with 10 mg/kg chrysin. The presence of ≥10 μM chrysin attenuated mesangial F-actin induction and bundle formation enhanced by AGE. Chrysin reduced the mesangial induction of α-smooth muscle actin (α-SMA) by glucose, and diminished the tissue α-SMA level in diabetic kidneys, indicating its blockade of mesangial proliferation. The treatment of chrysin inhibited the activation of vinculin and paxillin and the induction of cortactin, ARP2/3, fascin-1, and Ena/VASP-like protein in AGE-exposed mesangial cells. Oral administration of chrysin diminished tissue levels of cortactin and fascin-1 elevated in diabetic mouse kidneys. Mesangial cell motility was enhanced by AGE, which was markedly attenuated by adding chrysin to cells. On the other hand, chrysin dampened the induction of autophagy-related genes of beclin-1, LC3 I/II, Atg3, and Atg7 in mesangial cells exposed to AGE and in diabetic kidneys. Furthermore, chrysin reduced the mTOR activation in AGE-exposed mesangial cells and diabetic kidneys. The induction of mesangial F-actin, cortactin, and fascin-1 by AGE was deterred by the inhibition of autophagy and mTOR. Thus, chrysin may encumber diabetes-associated formation of actin bundling and focal adhesion and mesangial cell motility through disturbing autophagy and mTOR pathway.

Nutraceuticals and Diet-based Phytochemicals in Type 2 Diabetes Mellitus: From Whole Food to Components with Defined Roles and Mechanisms

BACKGROUND

Over the past decades, the development and use of an array of prescription medications have considerably improved the clinical management of type 2 diabetes mellitus and the quality of life of patients. However, as our knowledge of the associated risk factors and approaches to its management increases, the increasing roles of diet and the composition of the diet in the etiology and successful management of diabetes mellitus are being illuminated. Presently, a lot of attention is being given to nutraceuticals and certain phytochemicals that are integral parts of the human diet. It is believed that a clearer understanding of their roles may be crucial to 'non-invasive' or minimallyintrusive management, with regards to daily living of patients. In this review, an overview of nutraceutical components and phytochemicals that may be of benefit, or had been known to be beneficial in diabetes mellitus is given. Also, how the roles of such dietary components are evolving in the management of this disorder is highlighted. Lastly, the obstacles that need to be overcome before nutraceuticals can be considered as options for the clinical management of diabetes mellitus areconsidered.

CONCLUSION

Despite studies that demonstrate their efficacy, no nutraceutical or food-derived compound has been formally adopted as a direct replacement for any class of antidiabetic drugs.

Methylglyoxal induces retinopathy-type lesions in the absence of hyperglycemia: studies in a rat model

The aim of this study was to evaluate whether damage to the neurovascular unit in diabetes depends on reactive metabolites such as methylglyoxal (MG), and to assess its impact on retinal gene expression. Male Wistar rats were supplied with MG (50 mM) by drinking water and compared with age-matched streptozotocin-diabetic animals and untreated controls. Retinal damage was evaluated for the accumulation of MG-derived advanced glycation end products, changes in hexosamine and PKC pathway activation, microglial activation, vascular alterations (pericyte loss and vasoregression), neuroretinal function assessed by electroretinogram, and neurodegeneration. Retinal gene regulation was studied by microarray analysis, and transcription factor involvement was identified by upstream regulator analysis. Systemic application of MG by drinking water increased retinal MG to levels comparable with diabetic animals. Elevated retinal MG resulted in MG-derived hydroimidazolone modifications in the ganglion cell layer, inner nuclear layer, and outer nuclear layer, a moderate activation of the hexosamine pathway, a pan-retinal activation of microglia, loss of pericytes, increased formation of acellular capillaries, decreased function of bipolar cells, and increased expression of the crystallin gene family. MG mimics important aspects of diabetic retinopathy and plays a pathogenic role in microglial activation, vascular damage, and neuroretinal dysfunction. In response to MG, the retina induces expression of neuroprotective crystallins.-Schlotterer, A., Kolibabka, M., Lin, J., Acunman, K., Dietrich, N., Sticht, C., Fleming, T., Nawroth, P., Hammes, H.-P. Methylglyoxal induces retinopathy-type lesions in the absence of hyperglycemia: studies in a rat model.

Phytochemicals: Target-Based Therapeutic Strategies for Diabetic Retinopathy

Background: A variety of causative factors are involved in the initiation of diabetic retinopathy (DR). Current antidiabetic therapies are expensive and not easily accessible by the public. Furthermore, the use of multiple synthetic drugs leads to severe side effects, which worsen the diabetic patient’s condition. Medicinal plants and their derived phytochemicals are considered safe and effective treatment and their consumption can reduce the DR risk. In this article, we discuss a variety of medicinal plants, and their noteworthy bio-active constituents, that will be utilized as target based therapeutic strategies for DR. Methods: A broad-spectrum study was conducted using published English works in various electronic databases including Science Direct, PubMed, Scopus, and Google Scholar. Results: Targeting the multiple pathological factors including ROS, AGEs formation, hexosamine flux, PARP, PKC, and MAPK activation through variety of bioactive constituents in medicinal plants, diabetes progression can be delayed with improved loss of vision. Conclusions: Data reveals that traditional herbs and their prominent bioactive components control and normalize pathological cellular factors involved in DR progression. Therefore, studies should be carried out to explore the protective retinopathy effects of medicinal plants using experimental animal and humans models.

Cell surface expression of nucleolin mediates the antiangiogenic and antitumor activities of kallistatin

Kallistatin is a unique serine proteinase inhibitor and heparin-binding protein. A previous study conducted by our group indicated that kallistatin has antiangiogenic and antitumoral activities. In the present study, we report that kallistatin specifically binds to membrane surface-expressed nucleolin with high affinity. Antibody-mediated neutralization or siRNA-induced nucleolin knockdown results in loss of kallistatin suppression of endothelial cell proliferation and migration in vitro and tumor angiogenesis and growth in vivo. In addition, we show that kallistatin is internalized and transported into cell nuclei of endothelial cells via nucleolin. Within the nucleus, kallistatin inhibits the phosphorylation of nucleolin, which is a critical step required for cell proliferation. Thus, we demonstrate that nucleolin is a novel functional receptor of kallistatin that mediates its antiangiogenic and antitumor activities. These findings provide mechanistic insights into the inhibitory effects of kallistatin on endothelial cell growth, tumor cell proliferation, and tumor-related angiogenesis.

The Possible Role of Flavonoids in the Prevention of Diabetic Complications

Type 2 diabetes mellitus is a disease that affects many metabolic pathways. It is associated with insulin resistance, impaired insulin signaling, β-cell dysfunction, abnormal glucose levels, altered lipid metabolism, sub-clinical inflammation and increased oxidative stress. These and other unknown mechanisms lead to micro- and macro-complications, such as neuropathy, retinopathy, nephropathy and cardiovascular disease. Based on several in vitro animal models and some human studies, flavonoids appear to play a role in many of the metabolic processes involved in type 2 diabetes mellitus. In this review, we seek to highlight the most recent papers focusing on the relationship between flavonoids and main diabetic complications.

Patent Highlight

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

Suppression of antioxidant Nrf-2 and downstream pathway in H9c2 cells by advanced glycation end products (AGEs) via ERK phosphorylation

Diabetic cardiomyopathy is related to oxidative stress and correlated with the presence of advanced glycation end products (AGEs). In a clinical setting, AGEs can be detected in patients presenting diabetic cardiomyopathy; however, the underlying mechanism has yet to be elucidated. In our previous study, AGEs increase cell hypertrophy via ERK phosphorylation in a process closely related to ROS production. Thus, we propose that AGEs regulate the antioxidant gene nuclear factor-erythroid 2-related factor (Nrf-2). In H9c2 cells treated with AGEs, the expression of Nrf-2 was reduced; however, ERK phosphorylation was shown to increase. Treatment with H2O2 was also shown to increase Nrf-2 and ERK phosphorylation. In cells pretreatment with ROS scavenger NAC, the effects of H2O2 were reduced; however, the effects of the AGEs remained largely unchanged. Conversely, when cells were pretreated with PD98059 (ERK inhibitor), the expression of Nrf-2 was recovered following treatment with AGEs. Our results suggest that AGEs inhibit Nrf-2 via the ERK pathway; however, this influence is partly associated with ROS. Our finding further indicated that AGEs possess both ROS-dependent and ROS-independent pathways, resulting in a reduction in Nrf-2. This report reveals an important mechanism underlying the regulation of diabetic cardiomyopathy progression by AGEs.