Rat Kidney Aldose Reductase Research Articles

In vitro and in vivo evaluation of pterostilbene for the management of diabetic complications

BackgroundAldose reductase (AR) and Advanced glycation end product (AGE) are known to play important roles in the development of diabetic complications. The inhibitors of AR and AGE would be potential agents for the prevention of diabetic complications. ObjectiveThe present study was aimed to evaluate the aldose reductase (AR) and advanced glycation end product (AGE) inhibitory potential of pterostilbene for its possible role in the treatment of diabetic complications such as cataract. Materials and methodsThe compound was studied for its inhibitory activity against rat lens AR (RLAR) and rat kidney AR (RKAR) in vitro along with its ability to inhibit the formation of AGEs. Anticataract activity of pterostilbene was demonstrated using sugar induced lens opacity model in isolated cattle lens. Further, the involvement of pterostilbene in galactosemia in rats was investigated by assessing the key markers in the polyol pathway and the results were compared with that of a potent AR inhibitor, fidarestat. ResultsPterostilbene exhibited inhibitory activity against RLAR and RKAR with IC50 values of 5.49 mg/ml (21.4 mM) and 6.40 mg/ml (25.02 mM), respectively. In sugar-induced lens opacity model, pterostilbene displayed a significant protective effect by preventing opacification and formation of polyols in cattle lens. Besides, the compound exhibited in vivo inhibition of galactitol accumulation in lens and sciatic nerves of galactose fed rats. ConclusionThe results obtained in the study underline the potential of pterostilbene as possible therapeutic agent against long-term diabetic complications.

Inhibition behaviours of some phenolic acids on rat kidney aldose reductase enzyme: an in vitro study

Aldose reductase (AR) inhibitors have vital importance in the treatment and prevention of diabetic complications. In this study, rat kidney AR was purified 19.34-fold with a yield of 3.49% and a specific activity of 0.88 U/mg using DE-52 Cellulose anion exchange chromatography, gel filtration chromatography and 2′5′ ADP Sepharose-4B affinity chromatography, respectively. After purification, the in vitro inhibition effects of some phenolic acids (tannic acid, chlorogenic acid, sinapic acid, protocatechuic acid, 4-hydroxybenzoic acid, p-coumaric acid, ferulic acid, vanillic acid, syringic acid, α-resorcylic acid, 3-hydroxybenzoic acid and gallic acid) were investigated on purified enzyme. We determined IC50, Ki values and inhibition types of these phenolic acids. As a result, tannic and chlorogenic acid had a strong inhibition effect. On the other hand, gallic acid had a weak inhibition effect. In this study, all phenolic acids except for chlorogenic acid and p-coumaric acid showed non-competitive inhibition effects on rat kidney AR.

Evaluation of effect of alcoholic extract of heartwood of Pterocarpus marsupium on in vitro antioxidant, anti-glycation, sorbitol accumulation and inhibition of aldose reductase activity

Rising popularity of phytomedicines in various diseased conditions have strengthened the significance of plant-research and evaluation of phytoextracts in clinical manifestations. Pterocarpus marsupium Roxb., a medicinal plant, known for its anti-oxidant and anti-diabetic activity is a rich source of phytochemicals with antihyperglycemic and antihyperlipidemic activities. However, its possible role in diabetic complications is not evaluated yet. The present study explores the possible role of alcoholic extract of heartwood of P. marsupium in the treatment of long-term diabetic complications. The alcoholic extract of P. marsupium was evaluated for advanced glycation-end-products formation, erythrocyte sorbitol accumulation and rat kidney aldose reductase enzyme inhibition at the concentration of 25–400 μg/ml using in-vitro bioassays. Also the phytoextract at the concentration of 10–320 μg/ml was evaluated for its antioxidant potential by in-vitro antioxidant assays which includes, determination of total phenol content; reducing power assay; nitric oxide scavenging activity; superoxide radical scavenging activity; total antioxidant capacity; total flavonoid content; DPPH scavenging activity; and hydrogen peroxide scavenging activity.The alcoholic extract of P. marsupium across varying concentrations showed inhibitory effect as evident by IC50 on advanced glycation-end-products formation (55.39 μg/ml), sorbitol accumulation (151.00 μg/ml) and rat kidney aldose reductase (195.88 μg/ml). The phytoextract also exhibited high phenolic and flavonoid contents with promising antioxidant potential against the antioxidant assays evaluated. The present investigation suggests that the phytoextract showed prominent antioxidant, antiglycation property and, inhibited accumulation of sorbitol and ALR enzyme, thus promising a beneficial role in reducing/delaying diabetic complications.

Aldose Reductase Inhibitory and Antiglycation Activities of Four Medicinal Plant Standardized Extracts and Their Main Constituents for the Prevention of Diabetic Complications

The present study was intended to evaluate, highlight and explore the role of four medicinal plant ( Morus alba L., Phyllanthus amarus Schum. & Thonn., Punica granatum L., and Stevia rebaudiana Bertoni) standardized extracts and their major constituents (morusin, phyllanthin, punicalagin and stevioside) in the treatment of long-term diabetic complications by inhibition of aldose reductase (AR) enzyme and advanced glycation end products (AGEs) formation. Rat lens and kidney homogenates, which contain rat lens AR (RLAR) and rat kidney AR (RKAR) crude enzymes, respectively, prepared in the laboratory and commercially available human recombinant AR (HRAR) were used to carry out in vitro bioassays. AR inhibitory activity and inhibition of AGEs formation was done by using ultraviolet-visible (UV-Vis) and fluorescence spectroscopy with aminoguanidine as a standard. In vivo AR inhibitory activity, which involves determination of rat lens galactitol levels in galactosemic condition by using reverse phase high pressure liquid chromatography (RP-HPLC) and gas liquid chromatography (GLC) was determined. In the in vitro bioassays, punicalagin, the major constituent of P. granatum was found to have the most potent AR inhibitory activity with IC 50 values of 5.28, 6.22 and 4.70 μM in RLAR, RKAR, and HRAR assays, respectively, among the tested standardized extracts and pure compounds. Punicalagin (IC 50 = 5.11 μM), also inhibited generation of AGEs at a much lower concentration than that of the reference standard aminoguanidine (IC 50 = 50.47 μM). The effect of punicalagin in suppressing rat lens galactitol levels in galactose-fed rat model was also superior to all other studied compounds including the positive control quercetin. Standardized extracts of the plants and their major components have the potential to be used as capable shielding agents in therapy of diabetic complications; however, further studies are warranted to explain and explore their use in the treatment of diabetic complications. Keywords: Standardized Extracts, Aldose Reductase, Non-enzyme Maillard Reaction, Punicalagin, Galactitol Accumulation

Aldose Reductase Inhibitory Activity of Butea monosperma for the Management of Diabetic Complications

Background: Aldose Reductase (AR) enzyme and advanced glycation end products (AGEs) play an important role in diabetic complications. The AR and AGEs inhibitors are beneficial in prevention of diabetic complications. Objective: Aim of present study was to evaluate the in vitro and in vivo AR and AGEs inhibitory activity of an antidiabetic plant Butea monosperma. Methods: The methanolic extract, standardized extract of flower and the major constituent butein were studied for their inhibitory activity against Rat Lens AR (RLAR), rat kidney AR and generation of AGEs. In addition, in vivo inhibition of lens galactitol accumulation in galactose-fed rat model was studied. Results: The plant extracts and butein were shown to possess AR inhibitory activity in both in vitro and in vivo assays with equal potency to that of standard quercetin. In case of inhibited AGEs formation, the plant extracts showed insignificant activity where as butein was found to be potent. Conclusion: The results obtained in this study provide a new dimension to the hitherto unknown activity of the plant as possible protective agent against long-term diabetic complications.

Therapeutic potential of resveratrol in diabetic complications: In vitro and in vivo studies

BackgroundVarious mechanisms with a complex integrating paradigm have been implicated in diabetic complications. The present study was aimed to evaluate the aldose reductase (AR) and advanced glycation end products (AGEs) inhibitory activity of resveratrol (RSV) and its potential in the treatment of diabetic complications such as cataract and nephropathy. MethodsRSV was studied for its inhibitory activity against rat lens AR (RLAR) and rat kidney AR (RKAR) in vitro along with its ability to inhibit formation of AGEs. Anticataract activity of RSV was demonstrated using sugar induced lens opacity model in isolated cattle lens. Furthermore the involvement of RSV in streptozotocin-induced diabetic nephropathy was investigated by assessing the key markers of kidney function along with the formation of AGEs. The potent AR inhibitor, fidarestat was as a standard. ResultsRSV exhibited inhibitory activity against RLAR and RKAR with IC50 values of 4.99μg/ml (21.9μM) and 5.49μg/ml (24.5μM), respectively. It also showed a significant inhibition of AGEs formation in vitro. In sugar-induced lens opacity model, RSV displayed a significant protective effect preventing opacification and formation of polyols in cattle lens. RSV significantly improved glycaemic status and renal function in diabetic rats with a significant decrease in the formation of AGEs in the kidneys. ConclusionsThe results obtained in this study underline the potential of RSV as a possible therapeutic agent against long-term diabetic complications.

In Vitro and In Vivo Inhibitory Activities of Four Indian Medicinal Plant Extracts and their Major Components on Rat Aldose Reductase and Generation of Advanced Glycation Endproducts

The polyol enzyme aldose reductase (AR) and advanced glycation endproducts (AGEs) play an important role in diabetic complications such as cataracts. The purpose of this study was to investigate four standardized plant extracts used for the treatment of diabetes and related diseases, and their principal components for AR inhibitory activity and to find out their influence in diabetic complications. Thus, Boswellia serrata Triana & Planch. (Burseraceae), Lagerstroemia speciosa (L.) Pers. (Lythraceae), Ocimum gratissimum (L.) (Lamiaceae) and Syzygium cumin (L.) Skeels. (Myrthaceae) and their respective major constituents, boswellic acid, corosolic acid, ursolic acid and ellagic acid, were studied for their inhibitory activity against rat lens AR, rat kidney AR, human recombinant AR and generation of AGEs. In addition, in vivo inhibition of lens galactitol accumulation by the major constituents of the plants in galactose-fed rat has been studied. The results revealed that all the tested extracts and their active ingredients possess significant AR inhibitory actions in both in vitro and in vivo assays with urosolic acid showing the most potent effect. Furthermore, the study indicates the potential of the studied plants and their major constituents as possible protective agents against long-term diabetic complications.

Evaluation of rat kidney aldose reductase inhibitory activity of some N-acetyl dehydroalanine derivatives

Aldose reductase (AR) is an enzyme that catalyzes the conversion of glucose to sorbitol, which is in turn converted to fructose by sorbitol dehydrogenase. Increased AR activity has been implicated in the pathogenesis of diabetic complications such as neuropathy, nephropathy, retinopathy, and cataract. Inhibitors of AR thus seem to have the potential to prevent or treat diabetic complications. At present, however, side effects and/or insufficient pharmacokinetic profiles have made most of the drug candidates undesirable. In this study, the synthesis (l–o) and ARI activity of 15 N-acetyl dehydroalanine derivatives (a–o) are described. The synthesized compounds mainly contained aliphatic and aromatic side chains. The insertion of ethyl and chloro propyl side chains were shown to be more effective than the rest of the compounds. Between the synthesized compounds N-ethyl (b) and N-propylchloride (h) derivatives showed the best ARI activities.

The inhibitory effects of thiazolyl-2,4 thiazolidinedione compounds on the rat kidney aldose reductase enzyme

Aldoz redüktaz enzimi glukozun sorbitole indirgenmesi reaksiyonunda anahtar rol oynamaktadır. Sorbitolün birikimi diyabette, diyabetik katarakt, retinopati, nöropati ve nefropati gibi komplikasyonlara neden olmaktadır. Aldoz redüktaz inhibitörlerinin dokularda sorbitol birikimini önlediği gösterilmiştir. Aldoz redüktaz enziminin inhibisyonunun farmakolojik profilini geliştirmek amacı ile çok sayıda bileşik geliştirilmiştir. Bu çalışmada, tiyazolil-2,4-tiyazolidindion serilerinin (Ia-f, IIa-f and IIIa-f) aldoz redüktaz inhibitör aktiviteleri test edilmiştir. Substitüe-tiyazolil-tiyazolidindion türevlerinin çok az düzeyde inhibitör aktiviteleri olduğu tespit edilmiştir

Synthesis and biological activity of some new flavonyl-2,4-thiazolidinediones

A new series of flavonyl-2,4-thiazolidinediones ( Va– c, VIa– c) was prepared by Knoevenagel reaction. The synthesized compounds were tested for their ability to inhibit rat kidney aldose reductase (AR) and for their insulinotropic activities in INS-1 cells. Compound Vb was able to increase insulin release in the presence of 5.6 mmol/l glucose. Compounds VIa– c displayed moderate to high AR inhibitory activity levels. Particularly, compound VIa showed the highest AR inhibitory activity (86.57%).

In vitro aldose reductase inhibitory activity of some flavonyl-2,4-thiazolidinediones

Aldose reductase (AR) is implicated to play a critical role in diabetes and cardiovascular complications because of the reaction it catalyzes. AR enzyme appears to be the key factor in the reduction of glucose to sorbitol. Synthesis and accumulation of sorbitol in cells due to AR activity is the main cause of diabetic complications, such as diabetic cataract, retinopathy, neuropathy and nephropathy. Aldose reductase inhibitors have been found to prevent sorbitol accumulation in tissues. Numerous compounds have been prepared in order to improve the pharmacological prophile of inhibition of aldose reductase enzyme. In this study, seventeen flavonyl-2,4-thiazolidinediones (flavonyl-2,4-TZD) (Ia–e, IIa–e and IIIa–g) were tested for their ability to inhibit rat kidney AR. Compound Ib showed the highest inhibitory activity (88.69 ± 1.46%) whereas Ia, IIa, IIIa, IIIb also showed significant inhibitory activity (49.26 ± 2.85, 67.29 ± 1.09, 71.11 ± 1.95, 64.86 ± 1.21%, respectively).

Preliminary evaluation of rat kidney aldose reductase inhibitory activity of 2-phenylindole derivatives: affiliation to antioxidant activity

Diabetic complications including nephropathy, neuropathy, and cataract are leading causes of end-stage renal diseases and neurological disorders. Aldose reductase (AR), the rate-limiting enzyme of the polyol pathway, catalyzes the reduction of glucose to sorbitol via NADPH. Excessive accumulation of intracellular sorbitol found in various tissues of diabetic animals and in cells cultured under high glucose conditions has been proposed to be an important factor for the pathogenesis of diabetic complications. Indole ring–containing AR inhibitors have received considerable attention as potential treatments for diabetic complications. However, these agents have not achieved worldwide use because of limited efficacy or unacceptable adverse effects. In this study, a series of 2-phenylindole derivatives were evaluated via an in vitro spectrophotometric assay for their ability to inhibit rat kidney AR. In addition, the antioxidant and AR inhibitory activities of the compounds under study were compared.

Some new thiazolyl thiazolidinedione derivatives as aldose reductase inhibitors

In diabetes, increased flux through the polyol pathway has been implicated in the development of diabetic complications such as cataract, retinopathy, neuropathy, and nephropathy. Aldose reductase (AR) appears to be the key factor in the reduction of glucose to sorbitol. Aldose reductase inhibitors have been found to prevent sorbitol accumulation in tissues. A series of thiazolyl-2,4-thiazolidinediones was prepared by Knoevenagel reaction of substituted benzyl-2,4-thiazolidinediones with chlorothiazolecarbaldehydes and were evaluated for their ability to inhibit rat kidney AR by an in vitro spectrophotometric assay. Results showed that compounds containing piperidine at the C-2 position of thiazole ring showed better inhibitory activity than thiazole compounds having 4-chlorobenzylsulfanyl at the same position.

Screening and evaluation of rat kidney aldose reductase inhibitory activity of some pyridazine derivatives

Aldose reductase (AR) is an enzyme that catalyzes the conversion of glucose to sorbitol, which is in turn converted to fructose by sorbitol dehydrogenase. The increased glucose flux through this metabolic pathway has been linked to the development of diabetic complications such as neuropathy, nephropathy, retinopathy, and cataract. Inhibitors of AR thus seem to have the potential to prevent or treat diabetic complications. AR inhibitors belong to different chemical classes, one of which comprises pyridazinone analogues. At present, however, side effects and/or insufficient pharmacokinetic profiles have made most of the drug candidates undesirable. We evaluated a series of 2H-pyridazine-3-one and 6-chloropyridazine analogues via an in vitro spectrophotometric assay for their ability to inhibit rat kidney AR. The study showed that the introduction of a pyrazole ring on pyridazinone led to a marked decrease in AR inhibitory potency. Moreover, introduction of an acetic acid side chain on 2H-pyridazine-3-one and 6-chloropyridazine did not improve the AR inhibitory activity, which was an unexpected result. On the basis of preliminary AR inhibitory screening results on 2H-pyridazine-3-one and 6-chloropyridazine derivatives, we embarked on the synthesis of more derivatives to discover more active molecules.

Purification of human and rat kidney aldose reductase.

In the present study we report on a rapid two-step affinity chromatographic procedure to purify aldose reductase from human and rat kidney papilla and inner medulla. This enzyme, which is responsible for sorbitol formation in the kidney, was purified 145-fold from rat and 76-fold from human kidneys by consecutive Blue Sepharose and Matrex Orange chromatography. SDS-PAGE showed a single band of 38 kD for the human enzyme and a doublet of similar molecular weight for the rat kidney aldose reductase. The enzyme was characterized by substrate specificity and kinetic constants found identical to that of other organs purified previously.

Rat kidney aldose reductase and aldehyde reductase and polyol production in rat kidney

Mounting evidence indicates that aldose reductase catalyzed reduction of excess glucose to sorbitol initiates the onset of certain diabetic complications. However, the kidney contains a large amount of aldehyde reductase, another NADPH-dependent reductase. The study was designed to assess the importance of these reductases to sugar alcohol (polyol) production in the kidney. To study the ability to reduce aldoses to polyols, both aldose and aldehyde reductases were purified from rat kidneys. Incubation studies with purified enzymes clearly demonstrated the polyol formation by both enzymes. Galactose feeding induced polyol accumulation in both medulla and cortex of the rat kidney. Al 1576, a potent inhibitor of both enzymes, reduced this polyol accumulation in both cortex and medulla, while the selective inhibitors Ponalrestat or FK 366 resulted in greater inhibition in medulla than cortex. These results suggest that kidney polyols may be generated by both aldose and aldehyde reductases and that aldehyde reductase contributes to polyol production in the kidney cortex, the predominant site of diabetes-linked kidney lesions.

Gas chromatography of sugars and other polyhydroxy compounds

Aldose reductase (AR) and Advanced glycation end product (AGE) are known to play important roles in the development of diabetic complications. The inhibitors of AR and AGE would be potential agents for the prevention of diabetic complications.The present study was aimed to evaluate the aldose reductase (AR) and advanced glycation end product (AGE) inhibitory potential of pterostilbene for its possible role in the treatment of diabetic complications such as cataract.The compound was studied for its inhibitory activity against rat lens AR (RLAR) and rat kidney AR (RKAR) in vitro along with its ability to inhibit the formation of AGEs. Anticataract activity of pterostilbene was demonstrated using sugar induced lens opacity model in isolated cattle lens. Further, the involvement of pterostilbene in galactosemia in rats was investigated by assessing the key markers in the polyol pathway and the results were compared with that of a potent AR inhibitor, fidarestat.Pterostilbene exhibited inhibitory activity against RLAR and RKAR with IC50 values of 5.49 mg/ml (21.4 mM) and 6.40 mg/ml (25.02 mM), respectively. In sugar-induced lens opacity model, pterostilbene displayed a significant protective effect by preventing opacification and formation of polyols in cattle lens. Besides, the compound exhibited in vivo inhibition of galactitol accumulation in lens and sciatic nerves of galactose fed rats.The results obtained in the study underline the potential of pterostilbene as possible therapeutic agent against long-term diabetic complications.