Fibronectin glycation increases IGF-I induced proliferation of human aortic smooth muscle cells

Understanding the role of glycation in the pathology of various non-communicable diseases along with novel therapeutic strategies

Glycation refers to carbonyl group condensation of the reducing sugar with the free amino group of protein, which forms Amadori products and advanced glycation end products (AGEs). These AGEs alter protein structure and function by configuring a negative charge on the positively charged arginine and lysine residues. Glycation plays a vital role in the pathogenesis of metabolic diseases, brain disorders, aging, and gut microbiome dysregulation with the aid of 3 mechanisms: (i) formation of highly reactive metabolic pathway-derived intermediates, which directly affect protein function in cells, (ii) the interaction of AGEs with its associated receptors to create oxidative stress causing the activation of transcription factor NF-κB, and (iii) production of extracellular AGEs hinders interactions between cellular and matrix molecules affecting vascular and neural genesis. Therapeutic strategies are thus required to inhibit glycation at different steps, such as blocking amino and carbonyl groups, Amadori products, AGEs-RAGE interactions, chelating transition metals, scavenging free radicals, and breaking crosslinks formed by AGEs. The present review focused on explicitly elaborating the impact of glycation-influenced molecular mechanisms in developing and treating noncommunicable diseases.

Glycation-induced modification of tissue-specific ECM proteins: A pathophysiological mechanism in degenerative diseases

BACKGROUND

Glycation driven generation of advanced glycation end products (AGEs) and their patho-physiological role in human degenerative diseases has remained one of the thrust areas in the mainstream of disease biology. Glycation of extracellular matrix (ECM) proteins have deleterious effect on the mechanical and functional properties of tissues. Owing to the adverse pathophysiological concerns of glycation, there is a need to decipher the underlying mechanisms.

SCOPE OF REVIEW

AGE-modified ECM proteins affect the cell in the vicinity by altering protein structure-function, matrix-matrix or matrix-cell interaction and by activating signalling pathway through receptor for AGE. This review is intended for addressing the AGE-induced modification of tissue-specific ECM proteins and its implication in the pathogenesis of various organ-specific human ailments.

MAJOR CONCLUSIONS

The glycation affects the canonical cell behaviour due to alteration in the interaction of glycated ECM with receptors like integrins and discodin domain, and the signalling cues generated subsequently affect the downstream signalling pathways. Consequently, the variation of structural and functional properties of tissues due to matrix glycation helps in the initiation or progression of the disease condition.

GENERAL SIGNIFICANCE

This review offers comprehensive knowledge about the remodelling of glycation induced ECM and tissue-specific pathological concerns. As glycation of ECM affects the normal tissues and cell behaviour, the scientific discourse may also provide cues for developing candidate drugs that may help in attenuating the adverse effects of AGEs and perhaps open a research window of tailoring novel strategies for the management of glycation induced human degenerative diseases.

Effect of basal insulin therapy on vascular endothelial function and adipokine profiles in people with Type 2 diabetes

AIM

To compare the effects of the basal insulin analogues glargine and detemir on endothelial function and adipocytokine levels in people with Type 2 diabetes.

METHODS

We studied 32 people with Type 2 diabetes whose blood glucose control was unsatisfactory while receiving only oral hypoglycaemic drugs. Participants were randomized to either insulin glargine or detemir for 24 weeks and then crossed over to the other treatment without a washout period. Flow-mediated vasodilatation, adipocytokine levels (plasminogen activator inhibitor-1 and leptin/adiponectin ratio), and fasting ghrelin levels were monitored.

RESULTS

HbA_1c levels were significantly decreased by both basal insulin therapies. Body weight was significantly increased by glargine but not by detemir. The proportion of flow-mediated vasodilatation was significantly increased by detemir but not glargine (glargine: from 5.17 ± 0.69 to 5.94 ± 0.83%; detemir: from 4.89 ± 0.78 to 7.92 ± 0.69%). Plasminogen activator inhibitor-1 level was significantly decreased by only detemir (glargine: from 16.4 ± 1.8 to 17.3 ± 2.1; detemir: from 19.2 ± 2.8 to 16.0 ± 1.6 ng/ml). The leptin/adiponectin ratio was significantly increased only by glargine. Acyl ghrelin level was significantly decreased by glargine but not detemir.

CONCLUSIONS

These results suggest that the effect on endothelial function and adipocytokine profiles may differ between glargine and detemir in people with diabetes (Trial registration ID: UMIN000004973).

Advanced glycation end products impair the functions of saphenous vein but not thoracic artery smooth muscle cells through RAGE/MAPK signalling pathway in diabetes

Saphenous vein (SV) and internal thoracic artery (ITA) are commonly used bypass conduits. However, graft failure occurs in SV rather than in ITA, especially in diabetes (DM). The mechanism for this difference has not been fully understood. Accumulation of advanced glycation end products (AGEs) and activation of AGEs receptor (RAGE) could accelerate smooth muscle cells (SMC) proliferation in DM, we thus asked whether AGEs-RAGE could mediate the differences between SMC from SV (SMCV ) and from ITA (SMCA ). Twenty-five patients with DM and other 25 patients without DM were enclosed in DM and control group, respectively. AGEs (100 μg/ml) were added to cultured SMCA and SMCV obtained at coronary artery bypass graft (CABG) and proliferative rates were determined. Transcript expression, phosphorylation or protein expression levels of MAP kinase family (ERK, p38 and JNK), matrix metalloproteinases (MMP)-2 and MMP-9 were analysed by real-time PCR, Western-blot or immunofluorescence staining, respectively. Compared with paired SMCA , SMCV showed significantly increased proliferation rate, MAP kinase family phosphorylation, and MMP-2/9 expression in both groups, especially in DM group. The responses of SMCV induced by AGEs were significantly larger in DM than in control group, which could be suppressed by inhibition of RAGE and ERK. However, all the cellular events of SMCV were not found in paired SMCA . This study suggests that AGEs-RAGE could induce the proliferation of SMCV but not SMCA via MAP kinase pathway in DM. It is the intrinsic 'inactive' tendency of SMCA that contributes to the different rates of graft disease between SV and ITA after CABG.

TGFβ2 differentially modulates smooth muscle cell proliferation and migration in electrospun gelatin-fibrinogen constructs

A main goal of tissue engineering is the development of scaffolds that replace, restore and improve injured tissue. These scaffolds have to mimic natural tissue, constituted by an extracellular matrix (ECM) support, cells attached to the ECM, and signaling molecules such as growth factors that regulate cell function. In this study we created electrospun flat sheet scaffolds using different compositions of gelatin and fibrinogen. Smooth muscle cells (SMCs) were seeded on the scaffolds, and proliferation and infiltration were evaluated. Additionally, different concentrations of Transforming Growth Factor-beta2 (TGFβ2) were added to the medium with the aim of elucidating its effect on cell proliferation, migration and collagen production. Our results demonstrated that a scaffold with a composition of 80% gelatin-20% fibrinogen is suitable for tissue engineering applications since it promotes cell growth and migration. The addition of TGFβ2 at low concentrations (≤ 1 ng/ml) to the culture medium resulted in an increase in SMC proliferation and scaffold infiltration, and in the reduction of collagen production. In contrast, TGFβ2 at concentrations >1 ng/ml inhibited cell proliferation and migration while stimulating collagen production. According to our results TGFβ2 concentration has a differential effect on SMC function and thus can be used as a biochemical modulator that can be beneficial for tissue engineering applications.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.