Thermal aggregation of glycated bovine serum albumin

Aggregation and glycation processes in proteins have a particular interest in medicine fields and in food technology. Serum albumins are model proteins which are able to self-assembly in aggregates and also sensitive to a non-enzymatic glycation in cases of diabetes. In this work, we firstly reported a study on the glycation and oxidation effects on the structure of bovine serum albumin (BSA). The experimental approach is based on the study of conformational changes of BSA at secondary and tertiary structures by FTIR absorption and fluorescence spectroscopy, respectively. Secondly, we analysed the thermal aggregation process on BSA glycated with different glucose concentrations. Additional information on the aggregation kinetics are obtained by light scattering measurements. The results show that glycation process affects the native structure of BSA. Then, the partial unfolding of the tertiary structure which accompanies the aggregation process is similar both in native and glycated BSA. In particular, the formation of aggregates is progressively inhibited with growing concentration of glucose incubated with BSA. These results bring new insights on how aggregation process is affected by modification of BSA induced by glycation.     

Cyperus rotundus suppresses AGE formation and protein oxidation in a model of fructose-mediated protein glycoxidation

Non-enzymatic glycation, as the chain reaction between reducing sugars and the free amino groups of proteins, has been shown to correlate with severity of diabetes and its complications. Cyperus rotundus (Cyperaceae) is used both as a food to promote health and as a drug to treat certain diseases. In this study, considering the antioxidative effects of C. rotundus, we examined whether C. rotundus also protects against protein oxidation and glycoxidation. The protein glycation inhibitory activity of hydroalcoholic extract of C. rotundus was evaluated in vitro using a model of fructose-mediated protein glycoxidation. The C. rotundus extract with glycation inhibitory activity also demonstrated antioxidant activity when a ferric reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays as well as metal chelating activity were applied. Fructose (100 mM) increased fluorescence intensity of glycated bovine serum albumin (BSA) in terms of total AGEs during 14 days of exposure. Moreover, fructose caused more protein carbonyl (PCO) formation and also oxidized thiol groups more in glycated than in native BSA. The extract of C. rotundus at different concentrations (25–250 μg/ml) has significantly decreased the formation of AGEs in term of the fluorescence intensity of glycated BSA. Furthermore, we demonstrated the significant effect of C. rotundus extract on preventing oxidative protein damages including effect on PCO formation and thiol oxidation which are believed to form under the glycoxidation process. Our results highlight the protein glycation inhibitory and antioxidant activity of C. rotundus. These results might lead to the possibility of using the plant extract or its purified active components for targeting diabetic complications.     

Antiglycation and cell protective actions of metformin and glipizide in erythrocytes and monocytes

Chronic hyperglycaemia causes glycation which subsequently results in the long-term complications of diabetes. Albumin, the major plasma protein is more sensitive to glycation resulting in structural, biological and physiological modifications. The long-term benefits of commonly used anti-diabetic drugs such as metformin and glipizide in diabetic patients are well understood. However, no extensive study has been performed to assess their role in the glycation induced albumin modifications and cellular protection. We carried out the glycation of bovine serum albumin using methylglyoxal as a glycating agent in absence or presence of metformin and glipizide to establish their anti-glycation action. Different glycation markers (fructosamine, carbonyl groups, free thiol groups and β-amyloid aggregation) and protein structural markers (absorption spectroscopy and native-polyacrylamide gel electrophoresis) were examined. Further THP-1 cells (monocytes) and erythrocytes were treated with drugs that were exposed to glycated albumin samples for 24 h, respectively at 37 °C to investigate the cytoprotective actions of drugs against glycation. After the treatment different anti-oxidant indices (catalase, glutathione, superoxide dismutase and nitric oxide), cell viability, lipid peroxidation and erythrocyte hemolysis were determined. Treatment with metformin and glipizide during in vitro albumin glycation significantly reduced the formation of glycation adducts and inhibited structural modifications. They restored the level of antioxidants in THP-1 and erythrocytes cells treated with glycated albumin thus protecting cells. Our results suggested protection mode of albumin glycation through inhibition by metformin and glipizide. Additionally, they exerted inhibitory actions on glycation-induced cellular damage by restoring cellular antioxidant defense.     

Deciphering metal-induced oxidative damages on glycated albumin structure and function

Background

Metal ions such as copper or zinc are involved in the development of neurodegenerative pathologies and metabolic diseases such as diabetes mellitus. Albumin structure and functions are impaired following metal- and glucose-mediated oxidative alterations. The aim of this study was to elucidate effects of Cu(II) and Zn(II) ions on glucose-induced modifications in albumin by focusing on glycation, aggregation, oxidation and functional aspects.

Methods

Aggregation and conformational changes in albumin were monitored by spectroscopy, fluorescence and microscopy techniques. Biochemical assays such as carbonyl, thiol groups, albumin-bound Cu, fructosamine and amine group measurements were used. Cellular assays were used to gain functional information concerning antioxidant activity of oxidized albumins.

Results

Both metals promoted inhibition of albumin glycation associated with an enhanced aggregation and oxidation process. Metal ions gave rise to the formation of β-amyloid type aggregates in albumin exhibiting impaired antioxidant properties and toxic activity to murine microglia cells (BV2). The differential efficiency of both metal ions to inhibit albumin glycation, to promote aggregation and to affect cellular physiology is compared.

Conclusions and general significance

Considering the key role of oxidized protein in pathology complications, glycation-mediated and metal ion-induced impairment of albumin properties might be important parameters to be followed and fought.     

Ribosylation of bovine serum albumin induces ROS accumulation and cell death in cancer line (MCF-7)

Formation of advanced glycation end products (AGE) is crucially involved in the several pathophysiologies associated with ageing and diabetes, for example arthritis, atherosclerosis, chronic renal insufficiency, Alzheimer’s disease, nephropathy, neuropathy, and cataracts. Because of devastating effects of AGE and the significance of bovine serum albumin (BSA) as a transport protein, this study was designed to investigate glycation-induced structural modifications in BSA and their functional consequences in breast cancer cell line (MCF-7). We incubated d-ribose with BSA and monitored formation of d-ribose-glycated BSA by observing changes in the intensity of fluorescence at 410 nm. NBT (nitro blue tetrazolium) assay was performed to confirm formation of keto-amine during glycation. Absorbance at 540 nm (fructosamine) increased markedly with time. Furthermore, intrinsic protein and 8-anilino-1-naphthalenesulfonate (ANS) fluorescence revealed marked conformational changes in BSA upon ribosylation. In addition, a fluorescence assay with thioflavin T (ThT) revealed a remarkable increase in fluorescence at 485 nm in the presence of glycated BSA. This suggests that glycation with d-ribose induced aggregation of BSA into amyloid-like deposits. Circular dichroism (CD) study of native and ribosylated BSA revealed molten globule formation in the glycation pathway of BSA. Functional consequences of ribosylated BSA on cancer cell line, MCF-7 was studied by MTT assay and ROS estimation. The results revealed cytotoxicity of ribosylated BSA on MCF-7 cells.     

Influence of metal ions on thermal aggregation of bovine serum albumin: Aggregation kinetics and structural changes

Metal ions are implicated in protein aggregation processes of several neurodegenerative pathologies. In this work the effects of Cu(II) and Zn(II) ions on heat-induced structural modifications of bovine serum albumin (BSA) were studied, with the aim of delineating the role of these ions in the early stages of proteins aggregation kinetics. A joint application of different techniques was used. The aggregate growth was followed by dynamic light scattering measurements, whereas the conformational changes occurring in the protein structure were monitored by Raman and IR spectroscopy. Both in absence and in presence of metal ions, heating treatment gave rise to β-structures to the detriment of α-helix conformation of BSA. The temperature of protein unfolding was not sensitively affected by the presence of Zn(II) or Cu(II) ions; on the contrary, only Zn(II) ions slightly promoted the heat-induced aggregation of the protein, since bigger aggregates were formed in their presence. The different efficacy of the Cu(II) and Zn(II) ions in promoting the BSA aggregation were highlighted by Raman measurements, assessing the role of His residues in metal binding. A distinct polypeptide folding of the two metal-BSA systems takes place, since the predominant mode of metal binding depends on metal. In particular, in Zn-BSA the metal coordination involves the imidazole N_τ atom of His which can promote inter-molecular cross-linking.     

Kinetin inhibits protein oxidation and glycoxidation in vitro

We tested the ability of N(6)-furfuryladenine (kinetin) to protect against oxidative and glycoxidative protein damage generated in vitro by sugars and by an iron/ascorbate system. At 50 microM, kinetin was more efficient (82% inhibition) than adenine (49% inhibition) to inhibit the bovine serum albumin (BSA)-pentosidine formation in slow and fast glycation/glycoxidation models. Kinetin also inhibited the formation of BSA-carbonyls after oxidation significantly more than adenine did. However both compounds inhibited the advanced glycation end product (AGE) formation to the same extent (59-68% inhibition). At 200 microM, kinetin but not adenine, limited the aggregation of BSA during glycation. These data suggest that kinetin is a strong inhibitor of oxidative and glycoxidative protein-damage generated in vitro.     

Identification of preferential protein targets for carbonylation in human mature adipocytes treated with native or glycated albumin

Oxidative modifications in proteins can participate in the regulation of cellular functions and are frequently observed in numerous states of diseases. Albumin can undergo increased glycation during diabetes. An accumulation of oxidatively modified proteins in human mature adipocytes incubated with glycated albumin has previously been described. This study herein reports the identification of specifically carbonylated targets following separation of the cell proteins by 2D gels, Western blotting and mass spectrometry analyses. It identified eight oxidatively modified proteins, two of which (ACTB and Annexin A2) appeared as significantly more carbonylated in adipocytes treated with glycated albumin than with native albumin. Intracellular stress, evaluated in SW872 cell line, showed an impairment in the protective antioxidant action exerted by native BSA after the glycation of the protein. Decreased proteasome peptidase activities were found in glycated BSA-treated mature adipocytes. The data suggest an association of oxidative damage with the progression of diabetes disorders at the adipocytes level.     

Identification of preferential protein targets for carbonylation in human mature adipocytes treated with native or glycated albumin

Oxidative modifications in proteins can participate in the regulation of cellular functions and are frequently observed in numerous states of diseases. Albumin can undergo increased glycation during diabetes. An accumulation of oxidatively modified proteins in human mature adipocytes incubated with glycated albumin has previously been described. This study herein reports the identification of specifically carbonylated targets following separation of the cell proteins by 2D gels, Western blotting and mass spectrometry analyses. It identified eight oxidatively modified proteins, two of which (ACTB and Annexin A2) appeared as significantly more carbonylated in adipocytes treated with glycated albumin than with native albumin. Intracellular stress, evaluated in SW872 cell line, showed an impairment in the protective antioxidant action exerted by native BSA after the glycation of the protein. Decreased proteasome peptidase activities were found in glycated BSA-treated mature adipocytes. The data suggest an association of oxidative damage with the progression of diabetes disorders at the adipocytes level.     

Inhibition of amyloid aggregation of bovine serum albumin by sodium dodecyl sulfate at submicellar concentrations

Sodium dodecyl sulfate (SDS), as an anionic surfactant, can induce protein conformational changes. Recent investigations demonstrated different effects of SDS on protein amyloid aggregation. In the present study, the effect of SDS on amyloid aggregation of bovine serum albumin (BSA) was evaluated. BSA transformed to β-sheet-rich amyloid aggregates upon incubation at pH 7.4 and 65°C, as demonstrated by thioflavin T fluorescence, circular dichroism, and transmission electron microscopy. SDS at submicellar concentrations inhibited BSA amyloid aggregation with IC₅₀ of 47.5 μM. The inhibitory effects of structural analogs of SDS on amyloid aggregation of BSA were determined to explore the structure–activity relationship, with results suggesting that both anionic and alkyl moieties of SDS were critical, and that an alkyl moiety with chain length ≥10 carbon atoms was essential to amyloid inhibition. We attributed the inhibitory effect of SDS on BSA amyloid aggregation to interactions between the detergent molecule and the fatty acid binding sites on BSA. The bound SDS stabilized BSA, thereby inhibiting protein transformation to amyloid aggregates. This study reports for the first time that the inhibitory effect of SDS on albumin fibrillation is closely related to its alkyl structure. Moreover, the specific binding of SDS to albumin is the main driving force in amyloid inhibition. This study not only provides fresh insight into the role of SDS in amyloid aggregation of serum albumin, but also suggests rational design of novel antiamyloidogenic reagents based on specific-binding ligands.     

Assembly and function of the Photosystem II manganese stabilizing protein: lessons from its natively unfolded behavior

The Photosystem II (PS II) manganese stabilizing protein (MSP) possesses characteristics, including thermostability, ascribed to the natively unfolded class of proteins (Lydakis-Simantiris et al. (1999) Biochemistry 38: 404–414). A site-directed mutant of MSP, C28A, C51A, which lacks the -S–S- bridge, also binds to PS II at wild-type levels and reconstitutes oxygen evolution activity [Betts et al. (1996) Biochim Biophys Acta 1274: 135–142], although the mutant protein is even more disordered in solution. Both WT and C28A, C51A MSP aggregate upon heating, but an examination of the effects of protein concentration and pH on heat-induced aggregation showed that each MSP species exhibited greater resistance to aggregation at a pH near their pI (5.2) than do either bovine serum albumin (BSA) or carbonic anhydrase, which were used as model water soluble proteins. Increases in pH above the pI of the MSPs and BSA enhanced their aggregation resistance, a behavior which can be predicted from their charge (MSP) or a combination of charge and stabilization by -S–S- bonds (BSA). In the case of aggregation resistance by MSP, this is likely to be an important factor in its ability to avoid unproductive self-association reactions in favor of formation of the protein–protein interactions that lead to formation of the functional oxygen evolving complex.     

Formaldehyde-mediated aggregation of protein antigens: comparison of untreated and formalinized model antigens

A formaldehyde-mediated aggregation pathway (FMAP) is suggested as being primarily responsible for the aggregation of lyophilized tetanus toxoid (TT; a formalinized antigen) in the presence of moisture. The general occurrence of the FMAP was examined by using bovine serum albumin (BSA) and ribonuclease A (RNase) as model antigens; both protein antigens were formalinized according to a method commonly used to detoxify bacterial toxins. To clearly delineate the FMAP from other aggregation mechanisms, the aggregation kinetics and mechanism of both unmodified antigens (BSA and RNase) and formalinized antigens (f-BSA and f-RNase) were evaluated. We report that formaldehyde treatment introduces more rapid and extensive aggregation in antigens under conditions that favor the FMAP (i.e., 80% relative humidity and 37 degrees C). Consistent with formaldehyde-mediated crosslinking, f-antigen aggregates were covalent and non-disulfide-bonded, whereas BSA aggregates were disulfide-linked and RNase even did not aggregate under the same conditions. Coincorporation of amino acids (histidine and lysine), which strongly interact with formaldehyde, as well as prior antigen reduction with cyanoborohydride, significantly inhibited f-BSA aggregation, but showed no selective effect on BSA aggregation. Mechanistic analysis of f-BSA aggregates, inhibition studies, and similar reactivity of f-BSA with TT all confirmed the existence of the FMAP at moisture levels intermediate between the dry and solution state. This study demonstrates the potential for covalent reactions between formalinized protein antigens and neighboring chemical or biochemical species even after formalinization, and provides a general approach to inhibit the FMAP.     

Comparison of bovine serum albumin glycation by ribose and fructose in vitro and in vivo

Advanced glycation end products (AGEs) play a critical pathogenic role in the development of diabetic complications. Recent studies have shown that diabetes is associated with not only abnormal glucose metabolism but also abnormal ribose and fructose metabolism, although glucose is present at the highest concentration in humans. The glycation ability and contribution of ribose and fructose to diabetic complications remain unclear. Here, the glycation ability of ribose, fructose and glucose under a mimic physiological condition, in which the concentration of ribose or fructose was one-fiftieth that of glucose, was compared. Bovine serum albumin (BSA) was used as the working protein in our experiments. Ribose generated more AGEs and was markedly more cytotoxic to SH-SY5Y cells than fructose. The first-order rate constant of ribose glycation was found to be significantly greater than that of fructose glycation. LC-MS/MS analysis revealed 41 ribose-glycated Lys residues and 12 fructose-glycated residues. Except for the shared Lys residues, ribose reacted selectively with 17 Lys, while no selective Lys was found in fructose-glycated BSA. Protein conformational changes suggested that ribose glycation may induce BSA into amyloid-like monomers compared with fructose glycation. The levels of serum ribose were correlated positively with glycated serum protein (GSP) and diabetic duration in type 2 diabetes mellitus (T2DM), respectively. These results indicate that ribose has a greater glycation ability than fructose, while ribose largely contributes to the production of AGEs and provides a new insight to understand in the occurrence and development of diabetes complications.     

Interaction of Zinc, Ascorbic Acid, and Folic Acid in Glycation with Albumin as Protein Model

Using albumin as model, we conducted series of in vitro glycation experiments to examine role of zinc in glycation using glucose at 4–100 mg/ml, incubations at 37°C or 60°C, duration of 2 or 4 weeks and in presence of zinc or ascorbic acid (AA) or folic acid (FA). Modifications of bovine serum albumin (BSA) were examined by using fluorescence of advanced glycation end products (AGEs) and dityrosine, UV, and Fourier transformed infrared spectroscopy. Adding zinc (0 to 768.5 μmol/l) resulted in significant inhibition of albumin glycation by glucose with a linear fit, $ y = - 0.0{895}x + {23}0.{99}\left( {{R^2} = 0.{7676},p = 0.0{13}} \right) $ . The glycation by fructose was greater than that of glucose with stronger inhibitory effect by zinc in fructose–glycation (t?=??5.8, p?=?0.002). Addition of zinc significantly decreased fluorescence as seen in Zn?+?FA or Zn?+?AA sets as compared to sets of FA alone (p?=?0.00056) or AA alone (p?=?0.037). The fluorescence for dityrosine and AGE had a correlation of 0.897 (p?<?0.01). The data from fluorescence, UV, and FTIR spectra collectively suggested inhibitory effect of zinc in BSA glycation alone or in presence of FA and AA, showing new dimension for the protective action of zinc in hyperglycemic conditions.     

New insights into deleterious impacts of in vivo glycation on albumin antioxidant activities

Background

Albumin constitutes the most abundant circulating antioxidant and prevents oxidative damages. However, in diabetes, this plasmatic protein is exposed to several oxidative modifications, which impact on albumin antioxidant properties.

Methods

Most studies dealing on albumin antioxidant activities were conducted on in vitro modified protein. Here we tried to decipher whether reduced antioxidant properties of albumin could be evidenced in vivo. For this, we compared the antioxidant properties of albumin purified from diabetic patients to in vitro models of glycated albumin.

Results

Both in vivo and in vitro glycated albumins displayed impaired antioxidant activities in the free radical-induced hemolysis test. Surprisingly, the ORAC method (Oxygen Radical Antioxidant Capacity) showed an enhanced antioxidant activity for glycated albumin. Faced with this paradox, we investigated antioxidant and anti-inflammatory activities of our albumin preparations on cultured cells (macrophages and adipocytes). Reduced cellular metabolism and enhanced intracellular oxidative stress were measured in cells treated with albumin from diabetics. NF-kB –mediated gene induction was higher in macrophages treated with both type of glycated albumin compared with cells treated with native albumin. Anti inflammatory activity of native albumin is significantly impaired after in vitro glycation and albumin purified from diabetics significantly enhanced IL6 secretion by adipocytes. Expression of receptor for advanced glycation products is significantly enhanced in glycated albumin-treated cells.

Conclusions and general significance

Our results bring new evidences on the deleterious impairments of albumin important functions after glycation and emphasize the importance of in vivo model of glycation in studies relied to diabetes pathology.     

The glycation of albumin: structural and functional impacts

Oxidative stress and protein modifications are frequently observed in numerous disease states.Glucose constitutes a vital nutrient necessary to cellular oxygen metabolism. However, hyperglycemia-associated damage is an important factor in diabetes disorders.Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. From recent studies, it has become evident that protein glycation has important implications for protein activity, unfolding, and degradation, as well as for cell functioning.After giving a brief overview of the key role of albumin in overall antioxidant defense, this review examines its role as a target of glycation reactions. A synthesis of state of the art methods for measuring and characterizing albumin glycation is detailed. In light of recent data, we then report the impact of glycation on the structure of albumin and its various activities, especially its antioxidant and binding capacities. The biological impact of glycated albumin on cell physiology is also discussed, specifically the role of the protein as a biological marker of diabetes.     

Effects of oxidative modifications induced by the glycation of bovine serum albumin on its structure and on cultured adipose cells

Non-enzymatic glycosylation (glycation) and oxidative damages represent major research areas insofar as such modifications of proteins are frequently observed in numerous states of disease. Albumin undergoes structural and functional alterations, caused by increased glycosylation during non insulin-dependent diabetes mellitus, which is closely linked with the early occurrence of vascular complications. In this work, we first characterized structural modifications induced by the glycation of bovine serum albumin (BSA). A pathophysiological effect of glycated BSA was identified in primary cultures of human adipocytes as it induces an accumulation of oxidatively modified proteins in these cells. BSA was incubated in the presence or absence of physiological, pathological or supra-physiological concentrations of glucose at 37 degrees C for 7 weeks. Enhanced BSA glycation percentages were determined using boronate affinity columns. The occurrence of oxidative modifications was found to be enhanced in glycated BSA, after determination of the free thiol groups content, electrophoretic migration and infrared spectrometry spectra. An accumulation of carbonyl-modified proteins and an increased release of isoprostane were observed in cell media following the exposure of adipocytes to glycated albumin. These results provide a new possible mechanism for enhanced oxidative damages in diabetes.     

Aggregation kinetics of bovine serum albumin studied by FTIR spectroscopy and light scattering

To investigate which type of structural and conformational changes is involved in the aggregation processes of bovine serum albumin (BSA), we have performed thermal aggregation kinetics in D(2)O solutions of this protein. The tertiary conformational changes are followed by Amide II band, the secondary structural changes and the formation of beta-aggregates by the Amide I' band and, finally, the hydrodynamic radius of aggregates by dynamic light scattering. The results show, as a function of pD, that: tertiary conformational changes are more rapid as pD increases; the aggregation proceeds through formation of ordered aggregates (oligomers) at pD far from the isoelectric point of the protein; disordered structures add as the pD decreases. Moreover, beta-aggregates seem to contribute only to oligomers formation, as showed by the good correlation between kinetics of scattering intensity and IR absorption intensity. These results indicate for BSA a general mechanism of aggregation composed by partial unfolding of the tertiary structure and by the decrease of alpha-helix and random coil contents in favor of beta-sheet aggregates. This mechanism strictly depends on pD and gives rise to almost two distinct types of macromolecular aggregates.     

Quantitation of pH-induced Aggregation in Binary Protein Mixtures by Dielectric Spectroscopy

This paper presents a quantitative approach for measuring pH-controlled protein aggregation using dielectric spectroscopy. The technique is demonstrated through two aggregation experiments, the first between ??-lactoglobulin (??-Lg) and hen lysozyme (HENL) and the second between bovine serum albumin (BSA) and HENL. In both experiments, the formation of aggregates is strongly dependent on the solution pH and is clearly indicated by a decrease in the measured permittivity when the second protein is added. A quantifiable lower-bound on the ratio of proteins involved in the aggregation process is obtained from the permittivity spectra. Lower-bound aggregation ratios of 83?% for ??-Lg/HENL at pH?6.0 and 48?% for BSA/HENL at pH?9.2 were consistent with turbidity measurements made on the same solutions.     

Delay of diabetic cataract in rats by the antiglycating potential of cumin through modulation of alpha-crystallin chaperone activity

alpha-Crystallin, a molecular chaperone of the eye lens, plays an important role in maintaining the transparency of the lens by preventing the aggregation/inactivation of several proteins and enzymes in addition to its structural role. alpha-Crystallin is a long-lived protein and is susceptible to several posttranslational modifications during aging, more so in certain clinical conditions such as diabetes. Nonenzymatic glycation of lens proteins and decline in the chaperone-like function of alpha-crystallin have been reported in diabetic conditions. Therefore, inhibitors of nonenzymatic protein glycation appear to be a potential target to preserve the chaperone activity of alpha-crystallin and to combat cataract under hyperglycemic conditions. In this study, we investigated the antiglycating potential of cumin in vitro and its ability to modulate the chaperone-like activity of alpha-crystallin vis-à-vis the progression of diabetic cataract in vivo. Aqueous extract of cumin was tested for its antiglycating ability against fructose-induced glycation of goat lens total soluble protein (TSP), alpha-crystallin from goat lens and a nonlenticular protein bovine serum albumin (BSA). The antiglycating potential of cumin was also investigated by feeding streptozotocin (STZ)-induced diabetic rats with diet containing 0.5% cumin powder. The aqueous extract of cumin prevented in vitro glycation of TSP, alpha-crystallin and BSA. Slit lamp examination revealed that supplementation of cumin delayed progression and maturation of STZ-induced cataract in rats. Cumin was effective in preventing glycation of TSP and alpha-crystallin in diabetic lens. Interestingly, feeding of cumin to diabetic rats not only prevented loss of chaperone activity but also attenuated the structural changes of alpha-crystallin in lens. These results indicated that cumin has antiglycating properties that may be attributed to the modulation of chaperone activity of alpha-crystallin, thus delaying cataract in STZ-induced diabetic rats.