The complex landscape of intracellular signalling in protein modification under hyperglycaemic stress leading to metabolic disorders.

Hyperglycaemia is a life-threatening risk factor that occurs in both chronic and acute phases and has been linked to causing injury to many organs. Protein modification was triggered by hyperglycaemic stress, which resulted in pathogenic alterations such as impaired cellular function and tissue damage. Dysregulation in cellular function increases the condition associated with metabolic disorders, including cardiovascular diseases, nephropathy, retinopathy, and neuropathy. Hyperglycaemic stress also increases the proliferation of cancer cells. The major areas of experimental biomedical research have focused on the underlying mechanisms involved in the cellular signalling systems involved in diabetes-associated chronic hyperglycaemia. Reactive oxygen species and oxidative stress generated by hyperglycaemia modify many intracellular signalling pathways that result in insulin resistance and ß-cell function degradation. The dysregulation of post translational modification in ß cells is clinically associated with the development of diabetes mellitus and its associated diseases. This review will discuss the effect of hyperglycaemic stress on protein modification and the cellular signalling involved in it. The focus will be on the significant molecular changes associated with severe metabolic disorders.

Generation of autoantibodies against glycated fibrinogen: Role in diabetic nephropathy and retinopathy.

The process of glycation, characterized by the non-enzymatic reaction between sugars and free amino groups on biomolecules, is a key contributor to the development and progression of both microvascular and macrovascular complications associated with diabetes, particularly due to persistent hyperglycemia. This glycation process gives rise to advanced glycation end products (AGEs), which play a central role in the pathophysiology of diabetes complications, including nephropathy. The d-ribose-mediated glycation of fibrinogen plays a central role in the pathogenesis of diabetes nephropathy (DN) and retinopathy (DR) by the generation and accumulation of advanced glycation end products (AGEs). Glycated fibrinogen with d-ribose (Rb-gly-Fb) induces structural changes that trigger an autoimmune response by generating and exposing neoepitopes on fibrinogen molecules. The present research is designed to investigate the prevalence of autoantibodies against Rb-gly-Fb in individuals with type 2 diabetes mellitus (T2DM), DN & DR. Direct binding ELISA was used to test the binding affinity of autoantibodies from patients' sera against Rb-gly-Fb and competitive ELISA was used to confirm the direct binding findings by checking the bindings of isolated IgG against Rb-gly-Fb and its native conformer. In comparison to healthy subjects, 32% of T2DM, 67% of DN and 57.85% of DR patients' samples demonstrated a strong binding affinity towards Rb-gly-Fb. Both native and Rb-gly-Fb binding by healthy subjects (HS) sera were non-significant (p > 0.05). Furthermore, the early, intermediate, and end products of glycation have been assessed through biochemical and physicochemical analysis. The biochemical markers in the patient groups were also significant (p < 0.05) in comparison to the HS group. This study not only establishes the prevalence of autoantibodies against d-ribose glycated fibrinogen in DN but also highlights the potential of glycated fibrinogen as a biomarker for the detection of DN and/or DR. These insights may open new avenues for research into novel therapeutic strategies and the prevention of diabetes-related nephropathy and retinopathy.

A Perspective on the Impact of Advanced Glycation End Products in the Progression of Diabetic Nephropathy.

In 2007, diabetes affected around 244 million people across the globe. The number of diabetics worldwide is projected to reach 370 million by 2030. With diabetes incidence reaching epidemic proportions globally, diabetic nephropathy (DN) has emerged as one of the most difficult health conditions. Although therapeutic approaches such as rigorous blood glucose and blood pressure management are successful in preventing DN, they are far from ideal, and the number of diabetic patients with endstage renal disease continues to grow. As a result, a unique treatment approach for DN should be devised. There is mounting evidence that advanced glycation end products (AGEs), senescent macro protein derivatives generated at an accelerated pace in DN, contribute to DN by generating oxidative stress. The purpose of this article is to discuss the pathophysiological significance of AGEs and their receptor in DN.

Therapeutic Efficacy of Natural Product 'C-Phycocyanin' in Alleviating Streptozotocin-Induced Diabetes via the Inhibition of Glycation Reaction in Rats.

Diabetes is a long-term metabolic disorder characterized by persistently elevated blood sugar levels. Chronic hyperglycemia enhances glucose-protein interactions, leading to the formation of advanced glycation end products (AGEs), which form irreversible cross-links with a wide variety of macromolecules, and accumulate rapidly in the body tissues. Thus, the objective of this study was to assess the therapeutic properties of C-phycocyanin (C-PC) obtained from Plectonema species against oxidative stress, glycation, and type 2 diabetes mellitus (T2DM) in a streptozotocin (STZ)-induced diabetic Wistar rat. Forty-five days of C-PC administration decreased levels of triglycerides (TGs), blood glucose, glycosylated hemoglobin, (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), liver and kidney function indices, and raised body weight in diabetic rats. C-PC suppressed biochemical glycation markers, as well as serum carboxymethyllysine (CML) and fluorescent AGEs. Additionally, C-PC maintained the redox state by lowering lipid peroxidation and protein-bound carbonyl content (CC), enhancing the activity of high-density lipoprotein cholesterol (HDL-C) and renal antioxidant enzymes, and preserving retinal and renal histopathological characteristics. Thus, we infer that C-PC possesses antidiabetic and antiglycation effects in diabetic rats. C-PC may also act as an antidiabetic and antiglycation agent in vivo that may reduce the risk of secondary diabetic complications.

d-ribose-mediated glycation of fibrinogen: Role in the induction of adaptive immune response.

A nonenzymatic reaction between reducing sugars and amino groups of proteins results in the formation of advanced glycation end products, which are linked to a number of chronic progressive diseases with macro- and microvascular complications. In this research, we sought to ascertain the immunological response to d-ibose-glycated fibrinogen. New Zealand White female rabbits were immunized with native and d-ribose-glycated (Rb-gly-Fb) fibrinogen and used for studying the immunological response. Serum from these rabbits analyzed using direct binding and competitive inhibition ELISA was found to contain a high titer of antibodies against Rb-gly-Fb; Rb-gly-Fb was much more immunogenic than its native form. The IgG against Rb-gly-Fb (Rb-gly-Fb-IgG) was highly specific against the immunogenic protein. Moreover, histopathology and immunofluorescence studies revealed the deposition of the Rb-gly-Fb-IgG immune complex in the glomerular basement membrane of the kidneys of immunized rabbits. Furthermore, immunization with Rb-gly-Fb increased the expression of genes encoding proinflammatory cytokines, tumour necrosis factor α, interleukin-6, interleukin-1ß, and interferon-gamma, which is indicative of increased inflammation and the antigenic role of Rb-gly-Fb in provoking an immune response.

Physicochemical characterization of C-phycocyanin from Plectonema sp. and elucidation of its bioactive potential through in silico approach.

C-phycocyanin (C-PC), the integral blue-green algae (BGA) constituent has been substantially delineated for its biological attributes. Numerous reports have illustrated differential extraction and purification techniques for C-PC, however, there exists paucity in a broadly accepted process of its isolation. In the present study, we reported a highly selective C-PC purification and characterization method from nontoxic, filamentous and non-heterocystous cyanobacterium Plectonema sp. C-PC was extracted by freeze-thawing, desalted and purified using ion-exchange chromatography. The purity of C-PC along with its concentration was found to be 4.12 and 245 µg/ml respectively.  Comparative characterization of standard and purified C-PC was performed using diverse spectroscopic techniques namely Ultra Violet-visible, fluorescence spectroscopy and Fourier transform infrared (FT-IR). Sharp peaks at 620 nm and 350 nm with UV-visible and FT-IR spectroscopy respectively, confirmed amide I bands at around 1638 cm-1 (C=O stretching) whereas circular dichroism (CD) spectra exhibited α-helix content of secondary structure of standard 80.59% and 84.59% of column purified C-PC. SDS-PAGE exhibited two bands of α and ß subunits 17 and 19 kDa respectively. HPLC evaluation of purified C-PC also indicated a close resemblance of retention peak time (1.465 min, 1.234 min, 1.097 min and 0.905 min) with standard C-PC having retention peak timing of 1.448 min, 1.233 min and 0.925 min. As a cautious approach, the purified C-PC was further lyophilized to extend its shelf life as compared to its liquid isoform. To evaluate the bioactive potential of the purified C-PC in silico approach was attempted. The molecular docking technique was carried out of C-PC as a ligand-protein with free radicals and α-amylase, α-glucosidase, glycogen synthase kinase-3 and glycogen phosphorylase enzymes as receptors to predict the free radical scavenging (antioxidant) and to target antidiabetic property of C-PC. In both receptors free radicals and enzymes, ligand C-PC plays an important role in establishing interactions within the cavity of active sites. These results established the antioxidant potential of C-PC and also give a clue towards its antidiabetic potential warranting further research.

Glycation and Antioxidants: Hand in the Glove of Antiglycation and Natural Antioxidants.

The non-enzymatic interaction of sugar and protein resulting in the formation of advanced glycation end products responsible for cell signaling alterations ultimately leads to the human chronic disorders such as diabetes mellitus, cardiovascular diseases, cancer, etc. Studies suggest that AGEs upon interaction with receptors for advanced glycation end products (RAGE) result in the production of pro-inflammatory molecules and free radicals that exert altered gene expression effect. To date, many studies unveiled the potent role of synthetic and natural agents in inhibiting the glycation reaction at a lesser or greater extent. This review focuses on the hazards of glycation reaction and its inhibition by natural antioxidants, including polyphenols.