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Aging causes gradual changes in free radicals, antioxidants, and immune-imbalance in the elderly. This study aims to understand links among aging, gluco-oxidative stress, and autoantibodies in asymptomatic individuals. In vitro glycation of human serum albumin (Gly-HSA) induces appreciable biochemical changes. Significant inhibition of advanced glycation end products (AGEs) formation was achieved using garlic extract (53.75%) and epigallocatechin-3-gallate from green tea (72.5%). Increased amounts of serum carbonyl content (2.42 ± 0.5) and pentosidine (0.0321 ± 0.0029) were detected in IV-S (S represent smokers) vs. IV group individuals. Direct binding ELISA results exhibited significantly high autoantibodies against Gly-HSA in group IV-S (0.55 ± 0.054; p < 0.001) and III-S (0.40 ± 0.044; p < 0.01) individuals as compared to the age matched subjects who were non-smokers (group IV and III). Moreover, high average percent inhibition (51.3 ± 4.1%) was obtained against Gly-HSA in IV-S group individuals. Apparent association constant was found to be high for serum immunoglobulin-G (IgG) from group IV-S (1.18 × 10−6 M) vs. serum IgG from IV group (3.32 × 10−7 M). Aging induced gluco-oxidative stress and AGEs formation may generate neo-epitopes on blood-proteins, contributing to production of autoantibodies in the elderly, especially smokers. Use of anti-glycation natural products may reduce age-related pathophysiological changes.

The non-enzymatic glycosylation is a very common phenomenon in the physiological conditions which is mediated by distinct chemical entities containing reactive carbonyl species (RCS) and participate in the modification of various macromolecules particularly proteins. Till date, various carbonyl species, i.e., glucose, fructose, D-ribose and methylglyoxal have been used frequently to assess the in-vitro non-enzymatic glycosylation. Similarly, 2'-Deoxyribose is one of the most abundant reducing sugar of the living organisms which forms the part of deoxyribonucleic acid and may react with proteins leading to the production of glycation intermediates, advanced glycation end products (AGEs) and highly reactive RCS. Thymidine phosphorylase derived degradation of thymidine contributes to the formation of 2'-Deoxyribose, therefore, acting as a major source of cellular 2'-Deoxyribose. Since albumin is a major serum protein which plays various roles including binding and transporting endogenous and exogenous ligands, it is more prone to be modified through different physiological modifiers; therefore it may serve as a model protein for in-vitro experiments to study the effect of 2’Deoxyribose mediated modifications in the protein. In this study, Bovine Serum Albumin (BSA) was glycated with 50 and 100 mM 2'-Deoxyribose followed by examining secondary and tertiary structural modifications in BSA as compared to its native (unmodified) form by using various physicochemical techniques. We evident a significant modification in 2'-Deoxyribose-glycated BSA which was confirmed through increased hyperchromicity, keto amine moieties, carbonyl and hydroxymethyl furfural content, fluorescent AGEs, altered secondary structure conformers (α helix and β sheets), band shift in the amide-I region and diminished free lysine and free arginine content. These modifications were reported to be higher in 100 mM 2'-Deoxyribose-glycated BSA than 50 mM 2'-Deoxyribose-glycated BSA. Our findings also demonstrated that the rate of glycation is positively affected by the increased concentration of 2'-Deoxyribose. The results of the performed study can be implied to uncover the phenomenon of serum protein damage caused by 2'-Deoxyribose leading towards diabetic complications and number of AGE-related diseases.

Background: Depression and smoking contribute to the prognosis of autoimmune rheumatoid arthritis (RA). Advanced glycation end products (AGEs) are also detected in RA patients. This study correlates RA in patients with various levels of depression and a history of smoking through the detection of antibodies against AGEs of proteins. Methods: Sixty RA subjects were selected and divided into 4 groups based on their levels of depression and smoking habits. The division was as follows: group I consisted of RA patients classified as depressed (RA-D); group II consisted of RA patients with a history of smoking (RA-S); group III consisted of RA patients suffering from depression who were also smokers (RA-DS); and group IV consisted of patients with RA alone (RA-A), i.e., not depressed and non-smokers. In vitro human serum albumin (HSA) was modified by glucose, and the modifications were studied by biochemical and biophysical techniques. Glycated (G)-HSA was used as an antigen, and autoantibodies against G-HSA (G-HSA-Abs) were screened in serum samples of different groups of RA subjects. Oxidative stress levels in all patients and healthy individuals were analyzed by protein-bound carbonyl content estimations. Results: Significant biochemical and biophysical changes were detected in G-HSA when compared to native (N)-HSA. All patients and control subjects were screened for circulating G-HSA-Abs and N-HSA-Abs. From the cohort of different samples, serum autoantibodies from RA-DS showed a high recognition of G-HSA-Abs titres compared to RA-D or RA-S. RA-A exhibited the least binding of circulating G-HSA-Abs of all the groups. The oxidative stress marker, the carbonyl content also exhibited highest levels in RA-DS, followed by RA-D and RA-S. Band shift assay showed the highest titres of immunoglobulin G in the serum samples of RA-DS. Conclusions: Smoking and concomitant depression in RA subjects may lead to enhanced oxidative stress levels responsible for the gradual formation and/or exposing of cryptic epitopes on HSA that induce the production of G-HSA-Abs. Hence, we postulate that by reducing depression and corresponding oxidative stress, it may be possible to control or limit the severity of the precipitation of RA disease activity and improve prognosis.

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