Phloretin ameliorates diabetic nephropathy by inhibiting nephrin and podocin reduction through a non-hypoglycemic effect

Esculetin and Phloretin Combination Mitigates Acute Kidney Injury-Diabetes Comorbidity via Regulating Mitophagy and Inflammation: A Dual-Pronged Approach

Induction of PINK1/Parkin-mediated mitophagy and reducing inflammation via targeting the TLR4/NF-κB axis simultaneously could be a promising therapy for the complex pathophysiology of AKI-diabetes comorbidity. Earlier, esculetin by mitophagy activation and phloretin by inhibiting inflammation have shown promising renoprotection. Therefore, we aimed to evaluate the synergistic renoprotective ability of esculetin and phloretin combination against AKI-diabetes comorbidity. AKI-diabetes comorbidity was mimicked in vivo by bilateral ischemia/reperfusion injury (IRI) in diabetic rats and in vitro by sodium azide-induced hypoxia/reperfusion injury (HRI) under hyperglycemic conditions. The cells were pretreated with esculetin (50 μM) and phloretin (50 μM) for 24 h. Similarly, the diabetic AKI rats received esculetin (50 mg/kg/day, p.o.) and phloretin (50 mg/kg/day, p.o.) pretreatment for 4 days and 1 h before surgery. Further, the obtained samples were utilized for different experiments. Esculetin and phloretin in diabetic AKI rats preserved kidney function and prevented kidney injury, indicated by reduced plasma creatinine, blood urea nitrogen, and kidney injury molecule 1. Esculetin improved mitophagy, indicated by increased mitophagosome formation, increased PINK1, Parkin, LC3B, and decreased p62 expression. Similarly, phloretin suppressed the diabetic AKI-related increased expression of inflammatory mediators including NF-κB, TLR4, TNF-α, and MCP-1. Moreover, combination therapy showed a more pronounced effect via synergistically improving mitophagy, maintaining ΔΨm, preventing mitochondrial dysfunction, reducing inflammation, and apoptosis. Esculetin and phloretin combination ameliorated AKI-diabetes comorbidity more effectively than their monotherapies. Esculetin upregulated the PINK1/Parkin-mediated mitophagy, and phloretin reduced inflammation by inhibiting the TLR4/NF-κB axis, thereby synergistically preventing kidney dysfunction.

Network pharmacology combined with molecular docking and dynamics to assess the synergism of esculetin and phloretin against acute kidney injury-diabetes comorbidity

Acute kidney injury (AKI) is a global health concern with high incidence and mortality, where diabetes further worsens the condition. The available treatment options are not uniformly effective against the complex pathogenesis of AKI-diabetes comorbidity. Hence, combination therapies based on the multicomponent, multitarget approach can tackle more than one pathomechanism and can aid in AKI-diabetes comorbidity management. This study aimed to investigate the therapeutic potential of esculetin and phloretin combination against AKI-diabetes comorbidity by network pharmacology followed by validation by molecular docking and dynamics. The curative targets for diabetes, AKI, esculetin, and phloretin were obtained from DisGeNET, GeneCards, SwissTargetPrediction database. Further, the protein-protein interaction of the potential targets of esculetin and phloretin against AKI-diabetes comorbidity was investigated using the STRING database. Gene ontology and pathway enrichment analysis were performed with the help of the DAVID and KEGG databases, followed by network construction and analysis via Cytoscape. Molecular docking and dynamic simulations were performed to validate the targets of esculetin and phloretin against AKI-diabetes comorbidity. We obtained 6341 targets for AKI-diabetes comorbidity. Further, a total of 54 and 44 targets of esculetin and phloretin against AKI-diabetes comorbidity were retrieved. The top 10 targets for esculetin selected based on the degree value were AKR1B1, DAO, ESR1, PLK1, CA3, CA2, CCNE1, PRKN, HDAC2, and MAOA. Similarly, phloretin's 10 key targets were ACHE, CDK1, MAPK14, APP, CDK5R1, CCNE1, MAOA, MAOB, HDAC6, and PRKN. These targets were enriched in 58 pathways involved in the pathophysiology of AKI-diabetes comorbidity. Further, esculetin and phloretin showed an excellent binding affinity for these critical targets. The findings of this study suggest that esculetin and phloretin combination as a multicomponent multitarget therapy has the potential to prevent AKI-diabetes comorbidity.

A Systematic Review: Quercetin-Secondary Metabolite of the Flavonol Class, with Multiple Health Benefits and Low Bioavailability

The main goal of this systematic review on the flavonol class secondary metabolite quercetin is to evaluate and summarize the existing research on quercetin's potential health benefits, therapeutic properties, and effectiveness in disease prevention and treatment. In addition to evaluating quercetin's potential for drug development with fewer side effects and lower toxicity, this type of review attempts to collect scientific evidence addressing quercetin's roles as an antioxidant, anti-inflammatory, antibacterial, and anticancer agent. In the first part, we analyze various flavonoid compounds, focusing on their chemical structure, classification, and natural sources. We highlight their most recent biological activities as reported in the literature. Among these compounds, we pay special attention to quercetin, detailing its chemical structure, physicochemical properties, and process of biosynthesis in plants. We also present natural sources of quercetin and emphasize its health benefits, such as its antioxidant and anti-inflammatory effects. Additionally, we discuss methods to enhance its bioavailability, analyzing the latest and most effective delivery systems based on quercetin.

Astragaloside IV Alleviates Podocyte Injury in Diabetic Nephropathy through Regulating IRE-1α/NF-κ B/NLRP3 Pathway

OBJECTIVE

To investigate the effects of astragaloside IV (AS-IV) on podocyte injury of diabetic nephropathy (DN) and reveal its potential mechanism.

METHODS

In in vitro experiment, podocytes were divided into 4 groups, normal, high glucose (HG), inositol-requiring enzyme 1 (IRE-1) α activator (HG+thapsigargin 1 µmol/L), and IRE-1α inhibitor (HG+STF-083010, 20 µmol/L) groups. Additionally, podocytes were divided into 4 groups, including normal, HG, AS-IV (HG+AS-IV 20 µmol/L), and IRE-1α inhibitor (HG+STF-083010, 20 µmol/L) groups, respectively. After 24 h treatment, the morphology of podocytes and endoplasmic reticulum (ER) was observed by electron microscopy. The expressions of glucose-regulated protein 78 (GRP78) and IRE-1α were detected by cellular immunofluorescence. In in vivo experiment, DN rat model was established via a consecutive 3-day intraperitoneal streptozotocin (STZ) injections. A total of 40 rats were assigned into the normal, DN, AS-IV [AS-IV 40 mg/(kg·d)], and IRE-1α inhibitor [STF-083010, 10 mg/(kg·d)] groups (n=10), respectively. The general condition, 24-h urine volume, random blood glucose, urinary protein excretion rate (UAER), urea nitrogen (BUN), and serum creatinine (SCr) levels of rats were measured after 8 weeks of intervention. Pathological changes in the renal tissue were observed by hematoxylin and eosin (HE) staining. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to detect the expressions of GRP78, IRE-1α, nuclear factor kappa Bp65 (NF-κBp65), interleukin (IL)-1β, NLR family pyrin domain containing 3 (NLRP3), caspase-1, gasdermin D-N (GSDMD-N), and nephrin at the mRNA and protein levels in vivo and in vitro, respectively.

RESULTS

Cytoplasmic vacuolation and ER swelling were observed in the HG and IRE-1α activator groups. Podocyte morphology and ER expansion were improved in AS-IV and IRE-1α inhibitor groups compared with HG group. Cellular immunofluorescence showed that compared with the normal group, the fluorescence intensity of GRP78 and IRE-1α in the HG and IRE-1α activator groups were significantly increased whereas decreased in AS-IV and IRE-1α inhibitor groups (P<0.05). Compared with the normal group, the mRNA and protein expressions of GRP78, IRE-1α, NF-κ Bp65, IL-1β, NLRP3, caspase-1 and GSDMD-N in the HG group was increased (P<0.05). Compared with HG group, the expression of above indices was decreased in the AS-IV and IRE-1α inhibitor groups, and the expression in the IRE-1α activator group was increased (P<0.05). The expression of nephrin was decreased in the HG group, and increased in AS-IV and IRE-1α inhibitor groups (P<0.05). The in vivo experiment results revealed that compared to the normal group, the levels of blood glucose, triglyceride, total cholesterol, BUN, blood creatinine and urinary protein in the DN group were higher (P<0.05). Compared with DN group, the above indices in AS-IV and IRE-1α inhibitor groups were decreased (P<0.05). HE staining revealed glomerular hypertrophy, mesangial widening and mesangial cell proliferation in the renal tissue of the DN group. Compared with the DN group, the above pathological changes in renal tissue of AS-IV and IRE-1α inhibitor groups were alleviated. Quantitative RT-PCR and Western blot results of GRP78, IRE-1α, NF-κ Bp65, IL-1β, NLRP3, caspase-1 and GSDMD-N were consistent with immunofluorescence analysis.

CONCLUSION

AS-IV could reduce ERS and inflammation, improve podocyte pyroptosis, thus exerting a podocyte-protective effect in DN, through regulating IRE-1α/NF-κ B/NLRP3 signaling pathway.

A Review of Experimental Studies on Natural Chalcone-Based Therapeutic Targeting of Genes and Signaling Pathways in Type 2 Diabetes Complications

Diabetes mellitus type 2 (T2DM) is a common chronic condition that presents as unsettled hyperglycemia (HG) and results from insulin resistance (IR) and β-cell dysfunction. T2DM is marked by an increased risk of microvascular and macrovascular complications, all of which can be the cause of increasing mortality. Diabetic nephropathy (DNE), neuropathy (DNU), and retinopathy (DR) are the most common complications of diabetic microangiopathy, while diabetic cardiomyopathy (DCM) and peripheral vascular diseases are the major diabetic macroangiopathy complications. Chalcones (CHs) are in the flavonoid family and are commonly found in certain plant species as intermediate metabolites in the biosynthesis of flavonoids and their derivatives. Natural CHs with different substituents exert diverse therapeutic activities, including antidiabetic ones. However, the therapeutic mechanisms of natural CHs through influencing genes and/or signaling pathways in T2DM complications remain unknown. Therefore, this review summarizes the existing results from experimental models which highlight the mechanisms of natural CHs as therapeutic agents for T2DM complications.

Phloretin: a comprehensive review of its potential against diabetes and associated complications

OBJECTIVES

Phloretin is ubiquitous in apples (Malus domestica) and other fruits and has potential antidiabetic properties. Considering the preclinical potential of phloretin, its transition to clinical observations has unintentionally been neglected, particularly within the diabetic population. Furthermore, a comprehensive understanding of its pharmacokinetics remains elusive. This review seeks to offer valuable insights into phloretin's physical properties, pharmacokinetics, and pharmacodynamics, aiming to unveil opportunities for additional research on its therapeutic potential in the context of diabetes.

KEY FINDINGS

All pharmacokinetic reports of phloretin confirm that the utilization of phloretin gets enhanced during diabetic conditions. Phloretin targets pathomechanisms such as glucose transporter 4 (GLUT4) and peroxisome proliferator's activity-activated receptor-γ (PPAR-γ) to decrease insulin resistance in diabetic conditions. Moreover, phloretin targets inflammatory, oxidative, and apoptotic signaling to minimize the progression of diabetes-associated macro- and microvascular complications.

SUMMARY

The pleiotropic antidiabetic action of phloretin is mainly dependent on its pharmacokinetics. Nevertheless, further investigation into the altered pharmacokinetics of phloretin during diabetic conditions is essential. Additionally, the results derived from clinical studies utilized apples, apple extract, and supplements containing phloretin. Greater emphasis should be placed on future clinical studies to assess the potential of phloretin as a standalone compound.

Gallic Acid-Based Hydrogels for Phloretin Intestinal Release: A Promising Strategy to Reduce Oxidative Stress in Chronic Diabetes

Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia caused by abnormalities in insulin secretion and/or action. In patients with diabetes, complications such as blindness, delayed wound healing, erectile dysfunction, renal failure, heart disease, etc., are generally related to an increase in ROS levels which, when activated, trigger hyperglycemia-induced lesions, inflammation and insulin resistance. In fact, extensive cell damage and death occurs mainly due to the effect that ROS exerts at the level of cellular constituents, causing the deterioration of DNA and peroxidation of proteins and lipids. Furthermore, elevated levels of reactive oxygen species (ROS) and an imbalance of redox levels in diabetic patients produce insulin resistance. These destructive effects can be controlled by the defense network of antioxidants of natural origin such as phloretin and gallic acid. For this reason, the objective of this work was to create a nanocarrier (hydrogel) based on gallic acid containing phloretin to increase the antioxidant effect of the two substances which function as fundamental for reducing the mechanisms linked to oxidative stress in patients suffering from chronic diabetes. Furthermore, since the bioavailability problems of phloretin at the intestinal level are known, this carrier could facilitate its release and absorption. The obtained hydrogel was characterized using Fourier transform infrared spectroscopy (FT-IR). Its degree of swelling (a%) and phloretin release were tested under pH conditions simulating the gastric and intestinal environment (1.2, 6.8 and 7.4). The antioxidant activity, inhibiting lipid peroxidation in rat liver microsomal membranes induced in vitro by a free radical source, was evaluated for four hours. All results showed that gallate hydrogel could be applied for releasing intestinal phloretin and reducing the ROS levels.

Cytoskeleton Rearrangement in Podocytopathies: An Update

Podocyte injury can disrupt the glomerular filtration barrier (GFB), leading to podocytopathies that emphasize podocytes as the glomerulus's key organizer. The coordinated cytoskeleton is essential for supporting the elegant structure and complete functions of podocytes. Therefore, cytoskeleton rearrangement is closely related to the pathogenesis of podocytopathies. In podocytopathies, the rearrangement of the cytoskeleton refers to significant alterations in a string of slit diaphragm (SD) and focal adhesion proteins such as the signaling node nephrin, calcium influx via transient receptor potential channel 6 (TRPC6), and regulation of the Rho family, eventually leading to the disorganization of the original cytoskeletal architecture. Thus, it is imperative to focus on these proteins and signaling pathways to probe the cytoskeleton rearrangement in podocytopathies. In this review, we describe podocytopathies and the podocyte cytoskeleton, then discuss the molecular mechanisms involved in cytoskeleton rearrangement in podocytopathies and summarize the effects of currently existing drugs on regulating the podocyte cytoskeleton.

Oxidative stress and inflammation in diabetic nephropathy: role of polyphenols

Diabetic nephropathy (DN) often leads to end-stage renal disease. Oxidative stress demonstrates a crucial act in the onset and progression of DN, which triggers various pathological processes while promoting the activation of inflammation and forming a vicious oxidative stress-inflammation cycle that induces podocyte injury, extracellular matrix accumulation, glomerulosclerosis, epithelial-mesenchymal transition, renal tubular atrophy, and proteinuria. Conventional treatments for DN have limited efficacy. Polyphenols, as antioxidants, are widely used in DN with multiple targets and fewer adverse effects. This review reveals the oxidative stress and oxidative stress-associated inflammation in DN that led to pathological damage to renal cells, including podocytes, endothelial cells, mesangial cells, and renal tubular epithelial cells. It demonstrates the potent antioxidant and anti-inflammatory properties by targeting Nrf2, SIRT1, HMGB1, NF-κB, and NLRP3 of polyphenols, including quercetin, resveratrol, curcumin, and phenolic acid. However, there remains a long way to a comprehensive understanding of molecular mechanisms and applications for the clinical therapy of polyphenols.

Nutraceuticals and network pharmacology approach for acute kidney injury: A review from the drug discovery aspect

Acute kidney injury (AKI) has become a global health issue, with ~12 million reports yearly, resulting in a persistent increase in morbidity and mortality rates. AKI pathophysiology is multifactorial involving oxidative stress, mitochondrial dysfunction, epigenetic modifications, inflammation, and eventually, cell death. Hence, therapies able to target multiple pathomechanisms can aid in AKI management. To change the drug discovery framework from "one drug, one target" to "multicomponent, multitarget," network pharmacology is evolving as a next-generation research approach. Researchers have used the network pharmacology approach to predict the role of nutraceuticals against different ailments including AKI. Nutraceuticals (herbal products, isolated nutrients, and dietary supplements) belong to the pioneering category of natural products and have shown protective action against AKI. Nutraceuticals have recently drawn attention because of their ability to provide physiological benefits with less toxic effects. This review emphasizes the nutraceuticals that exhibited renoprotection against AKI and can be used either as monotherapy or adjuvant with conventional therapies to boost their effectiveness and lessen the adverse effects. Additionally, the study sheds light on the application of network pharmacology as a cost-effective and time-saving approach for the therapeutic target prediction of nutraceuticals against AKI.

Loss of Sirt1 promotes exosome secretion from podocytes by inhibiting lysosomal acidification in diabetic nephropathy

Podocyte injury is a characteristic feature of diabetic nephropathy (DN). The secretion of exosomes in podocytes increases significantly in DN; however, the precise mechanisms remain poorly understood. Here, we demonstrated that Sirtuin1 (Sirt1) was significantly downregulated in podocytes in DN, which correlated negatively with increased exosome secretion. Similar results were observed in vitro. We found that lysosomal acidification in podocytes following high glucose administration was markedly inhibited, resulting in the decreased lysosomal degradation of multivesicular bodies. Mechanistically, we indicated that loss of Sirt1 contributed to the inhibited lysosomal acidification by decreasing the expression of the A subunit of the lysosomal vacuolar-type H⁺ ATPase proton pump (ATP6V1A) in podocytes. Overexpression of Sirt1 significantly improved lysosomal acidification with increased expression of ATP6V1A and inhibited exosome secretion. These findings suggest that dysfunctional Sirt1-mediated lysosomal acidification is the exact mechanism of increased secretion of exosomes in podocytes in DN, providing insights into potential therapeutic strategies for preventing DN progression.

Transdermal Delivery of Phloretin by Gallic Acid Microparticles

Exposure to ultraviolet (UV) radiation causes harmful effects on the skin, such as inflammatory states and photoaging, which depend strictly on the form, amount, and intensity of UV radiation and the type of individual exposed. Fortunately, the skin is endowed with a number of endogenous antioxidants and enzymes crucial in its response to UV radiation damage. However, the aging process and environmental stress can deprive the epidermis of its endogenous antioxidants. Therefore, natural exogenous antioxidants may be able to reduce the severity of UV-induced skin damage and aging. Several plant foods constitute a natural source of various antioxidants. These include gallic acid and phloretin, used in this work. Specifically, polymeric microspheres, useful for the delivery of phloretin, were made from gallic acid, a molecule that has a singular chemical structure with two different functional groups, carboxylic and hydroxyl, capable of providing polymerizable derivatives after esterification. Phloretin is a dihydrochalcone that possesses many biological and pharmacological properties, such as potent antioxidant activity in free radical removal, inhibition of lipid peroxidation, and antiproliferative effects. The obtained particles were characterized by Fourier transform infrared spectroscopy. Antioxidant activity, swelling behavior, phloretin loading efficiency, and transdermal release were also evaluated. The results obtained indicate that the micrometer-sized particles effectively swell, and release the phloretin encapsulated in them within 24 h, and possess antioxidant efficacy comparable to that of free phloretin solution. Therefore, such microspheres could be a viable strategy for the transdermal release of phloretin and subsequent protection from UV-induced skin damage.

Naringin abrogates angiotensin-converting enzyme (ACE) activity and podocin signalling pathway in cobalt chloride-induced nephrotoxicity and hypertension

PurposeThe persistent and alarming rates of increase in cardiovascular and renal diseases caused by chemicals such as cobalt chloride (CoCl₂) in mammalian tissues have led to the use of various drugs for the treatment of these diseases. This study aims at evaluating the nephron-protective action of Naringin (NAR), a metal-chelating antioxidant against CoCl₂-induced hypertension and nephrotoxicity.MethodsForty-two male Wistar rats were randomly distributed to seven rats of six groups and classified into Group A (Control), Group B (300 part per million; ppm CoCl₂), Group C (300 ppm CoCl₂ + 80 mg/kg NAR), Group D (300 ppm CoCl₂ + 160 mg/kg NAR), Group E (80 mg/kg NAR), and Group F (160 mg/kg NAR). NAR and CoCl₂ were administered via oral gavage for seven days. Biomarkers of renal damage, oxidative stress, antioxidant status, blood pressure parameters, immunohistochemistry of renal angiotensin-converting enzyme and podocin were determined.ResultsCobalt chloride intoxication precipitated hypertension, renal damage, and oxidative stress. Immunohistochemistry revealed higher expression of angiotensin-converting enzyme (ACE) and podocin in rats administered only CoCl₂.ConclusionTaken together, the antioxidant and metal-chelating action of Naringin administration against cobalt chloride-induced renal damage and hypertension could be through abrogation of angiotensin-converting enzyme and podocin signalling pathway.

The Molecular Pharmacology of Phloretin: Anti-Inflammatory Mechanisms of Action

The isolation of phlorizin from the bark of an apple tree in 1835 led to a flurry of research on its inhibitory effect on glucose transporters in the intestine and kidney. Using phlorizin as a prototype drug, antidiabetic agents with more selective inhibitory activity towards glucose transport at the kidney have subsequently been developed. In contrast, its hydrolysis product in the body, phloretin, which is also found in the apple plant, has weak antidiabetic properties. Phloretin, however, displays a range of pharmacological effects including antibacterial, anticancer, and cellular and organ protective properties both in vitro and in vivo. In this communication, the molecular basis of its anti-inflammatory mechanisms that attribute to its pharmacological effects is scrutinised. These include inhibiting the signalling pathways of inflammatory mediators' expression that support its suppressive effect in immune cells overactivation, obesity-induced inflammation, arthritis, endothelial, myocardial, hepatic, renal and lung injury, and inflammation in the gut, skin, and nervous system, among others.

Therapeutic Potential and Pharmaceutical Development of a Multitargeted Flavonoid Phloretin

Phloretin is a flavonoid of the dihydrogen chalcone class, present abundantly in apples and strawberries. The beneficial effects of phloretin are mainly associated with its potent antioxidant properties. Phloretin modulates several signaling pathways and molecular mechanisms to exhibit therapeutic benefits against various diseases including cancers, diabetes, liver injury, kidney injury, encephalomyelitis, ulcerative colitis, asthma, arthritis, and cognitive impairment. It ameliorates the complications associated with diabetes such as cardiomyopathy, hypertension, depression, memory impairment, delayed wound healing, and peripheral neuropathy. It is effective against various microbial infections including Salmonella typhimurium, Listeria monocytogenes, Mycobacterium tuberculosis, Escherichia coli, Candida albicans and methicillin-resistant Staphylococcus aureus. Considering the therapeutic benefits, it generated interest for the pharmaceutical development. However, poor oral bioavailability is the major drawback. Therefore, efforts have been undertaken to enhance its bioavailability by modifying physicochemical properties and molecular structure, and developing nanoformulations. In the present review, we discussed the pharmacological actions, underlying mechanisms and molecular targets of phloretin. Moreover, the review provides insights into physicochemical and pharmacokinetic characteristics, and approaches to promote the pharmaceutical development of phloretin for its therapeutic applications in the future. Although convincing experimental data are reported, human studies are not available. In order to ascertain its safety, further preclinical studies are needed to encourage its pharmaceutical and clinical development.