Clinical potential of advanced glycation end-product inhibitors in diabetes mellitus

Instantaneous Hydrolysis of Methyl Paraoxon Nerve Agent Simulant Is Catalyzed by Nontoxic Aminoguanidine Imines

Exposure to organophosphate-based nerve agents and pesticides poses health and security threats to civilians, soldiers, and first responders. Thus, there is a need to develop effective decontamination agents that are nonhazardous to human health. To address this, we demonstrate that instantaneous hydrolysis of methyl paraoxon (Me-POX), a nerve agent simulant, can be achieved in the presence of aminoguanidine imines at pH 10: ● the pyridine-4-aldehyde aminoguanidine-imine (1) and ● the 2,3-butanedione aminoguanidine-imine (2). The hydrolysis of Me-POX under these conditions is substantially faster than that of the state-of-the-art decontaminating agent, Dekon-139 (2,3-butanedione oxime, potassium salt). Furthermore, Dekon-139 shows adverse effects when applied on skin surfaces, making it of great interest to develop safer but effective decontaminating agents for neutralizing nerve agents and pesticides exposed to skin-surface areas. Our pharmaceutically relevant aminoguanidine derivatives serve as rather nontoxic and safe decontaminating agents for organophosphate-based nerve agents and pesticides. The hydrolytic degradation products of Me-POX by our aminoguanidine-based imines and Dekon-139 are pH dependent. At pH > 10, Me-POX is hydrolyzed to give dimethyl phosphate as the exclusive product, whereas at pH < 9, the major product of hydrolysis is methyl 4-nitrophenyl phosphate (M4NP). We applied Quantum Mechanics calculations to investigate the mechanism of this dramatically accelerated decontamination process. We predict that in the rate-determining transition state, both 1 and 2 stabilize the reaction center through hydrogen bonding. Compared to Dekon-139, the rate constants of the rate-determine steps (RDS) are predicted to be over 9,000 times larger for 1 and over 600 times larger for 2, explaining the improvement. Quantum Mechanics calculations rationalize the pH-dependent hydrolysis products of the Me-POX in the gas phase, and gauge-including atomic orbital (GIAO)-31P NMR chemical shift calculations confirm the experimental values.

The impact of diabetes mellitus on tendon pathology: a review

Diabetes is one of the most common metabolic diseases worldwide, leading to complications, mortality, and significant healthcare expenditures, which impose a substantial social and financial burden globally. A diabetic environment can induce metabolic changes, negatively affecting tendon homeostasis, leading to alterations in biomechanical properties and histopathology. Numerous studies have investigated the mechanisms through which diabetes exerts pathological effects on tendons, including increased free radical production, oxidative stress, inflammatory responses, deposition of advanced glycation end products (AGEs), and microvascular changes. These metabolic changes damages tendon structure, biomechanics, and tendon repair processes. The proliferation of tendon stem cells decreases, apoptosis increases, and abnormal differentiation, along with abnormal expression of myofibroblasts, ultimately lead to insufficient tendon repair, fibrosis, and remodeling. Although researches unveiling the effects of diabetes on tendinopathy, fibrosis or contracture, and tendon injury healing are growing, systematic understanding is still lacking. Therefore, this review summarizes the current research status and provides a comprehensive overview, offering theoretical guidance for future in-depth exploration of the impact of diabetes on tendons and the development of treatments for diabetes-related tendon diseases.

Small molecule inhibiting microglial nitric oxide release could become a potential treatment for neuroinflammation

Microglia are the immune effector cells of the central nervous system (CNS) and react to pathologic events with a complex process including the release of nitric oxide (NO). NO is a free radical, which is toxic for all cells at high concentrations. To target an exaggerated NO release, we tested a library of 16 544 chemical compounds for their effect on lipopolysaccharide (LPS)-induced NO release in cell line and primary neonatal microglia. We identified a compound (C1) which significantly reduced NO release in a dose-dependent manner, with a low IC50 (252 nM) and no toxic side effects in vitro or in vivo. Target finding strategies such as in silico modelling and mass spectroscopy hint towards a direct interaction between C1 and the nitric oxide synthase making C1 a great candidate for specific intra-cellular interaction with the NO producing machinery.

What Every Diabetologist Should Know about SARS-CoV-2: State of Knowledge at the Beginning of 2021

For almost a year, the major medical problem has been the pandemic caused by the SARS-CoV-2 virus. People with diabetes who contract COVID-19 are likely to experience more serious symptoms than patients without diabetes. This article presents new research about the epidemiology of COVID-19 in a group of patients with diabetes. It details the mortality and prognosis in such patients, as well as the relationship between COVID-19 and the diseases most often coexisting with diabetes: obesity, atherosclerosis, hypertension, and increased risk for infection. It also details how the virus infects and affects patients with hyperglycemia. The context of glycation and receptors for advanced glycation products (RAGE) seems to be of particular importance here. We also present a hypothesis related to the cause-and-effect axis-it turns out that diabetes can be both the cause of the more difficult course of COVID-19 and the result of SARS-CoV-2 infection. The last part of this article discusses the impact of antihyperglycemic drugs on the development of COVID-19 and other pharmacological implications, including which non-classical antihyperglycemic drugs seem to be effective in both the treatment of coronavirus infection and glucose homeostasis, and what strategies related to RAGE and glycation should be considered.

Identification of pheophorbide a as an inhibitor of receptor for advanced glycation end products in Mallotus japonicus

Accumulation of advanced glycation end products (AGEs) plays an important role in diabetes, immunoinflammation, and cardiovascular and neurodegenerative diseases. Since AGEs mediate their pathological effects through interaction with receptor for AGEs (RAGE), RAGE antagonists would provide a useful therapeutic option for various health disorders. Therefore, in this study, we aimed to identify phytochemicals that would inhibit binding of AGEs to RAGE, which may help develop new drug leads and/or nutraceuticals for AGE-RAGE-related diseases. On screening ethanol extracts obtained from 700 plant materials collected in Myanmar, we found that the ethanol extract from the leaves of Mallotus philippensis inhibited the binding of AGEs to RAGE. We also found that the leaves of M. japonicus, which belongs to the same genera and distributes abundantly in Japan, exhibited the inhibitory activity similar to M. philippensis. Activity-guided fractionation and LC/MS analysis of the ethanol extract of M. japonicus helped identify pheophorbide a (PPBa) as a major component in the active fraction, along with some other pheophorbide derivatives. PPBa exhibited potent inhibitory activity against AGE-RAGE binding, with an IC₅₀ value (0.102 μM) comparable to that of dalteparin (0.084 μM). PPBa may be a valuable natural product for use as a therapeutic agent and/or a nutraceutical against various health complications arising from activation of the AGE-RAGE axis.

Soluble receptor for advanced glycation end products in multiple sclerosis: a potential marker of disease severity

OBJECTIVES

To compare serum levels of the receptor for advanced glycation end products (sRAGE) between multiple sclerosis (MS) patients and healthy control subjects, and to investigate whether serum sRAGE levels correlate with MS disease severity as indicated by the Kurtzke Expanded Disability Status Scale (EDSS).

METHOD

37 patients with clinical diagnosis of MS and 22 healthy control subjects were investigated in a cross-sectional study using enzyme-linked immunosorbent assays (ELISA).

RESULTS

Serum levels of sRAGE were found to be significantly lower in MS patients compared to levels in healthy controls (p = 0.005). A trend toward lower levels of serum sRAGE was observed in female MS patients compared to their male counterparts (p = 0.05). A relationship between sRAGE and EDSS, and sRAGE and rate of clinical relapse was observed (p = 0.012).

CONCLUSION

The significant reduction of sRAGE in MS patients relative to healthy controls supports the potential role for RAGE axis in MS clinical pathology. Lower levels of sRAGE may be associated with enhanced inflammatory responses. Based on these observations, further investigations into the role of sRAGE in MS clinical pathology is warranted.

Targeting the retinal microcirculation to treat diabetic sight problems

Diabetic retinopathy is a secondary complication of hyperglycemia caused by diabetes mellitus. The damage to the retina can ultimately cause vision loss as a result of increased capillary permeability and angiogenesis. Recent progress in the understanding of the mediators that drive angiogenesis, as well as the phenotypes of cells that are involved in this process, has provided a multitude of targets for pharmacologic intervention. This review presents the inhibitors of the biochemical processes that are at the root of diabetic retinopathy (i.e., non-enzymatic glycosylation of biomolecules, oxidative stress, activation of aldose reductase and activation of protein kinase C by formation of diacylglycerol) in addition to the inhibitors of the mechanical damage (i.e., increased vascular permeability, capillary occlusion and neovascularization).

Advanced glycation end products and the kidney

Advanced glycation end products (AGEs) are a heterogeneous group of protein and lipids to which sugar residues are covalently bound. AGE formation is increased in situations with hyperglycemia (e.g., diabetes mellitus) and is also stimulated by oxidative stress, for example in uremia. It appears that activation of the renin-angiotensin system may contribute to AGE formation through various mechanisms. Although AGEs could nonspecifically bind to basement membranes and modify their properties, they also induce specific cellular responses including the release of profibrogenic and proinflammatory cytokines by interacting with the receptor for AGE (RAGE). However, additional receptors could bind AGEs, adding to the complexity of this system. The kidney is both: culprit and target of AGEs. A decrease in renal function increases circulating AGE concentrations by reduced clearance as well as increased formation. On the other hand, AGEs are involved in the structural changes of progressive nephropathies such as glomerulosclerosis, interstitial fibrosis, and tubular atrophy. These effects are most prominent in diabetic nephropathy, but they also contribute to renal pathophysiology in other nondiabetic renal diseases. Interference with AGE formation has therapeutic potential for preventing the progression of chronic renal diseases, as shown from data of animal experiments and, more recently, the first clinical trials.

Vascular complications in diabetes mellitus: the role of endothelial dysfunction

The endothelium is a complex organ with a multitude of properties essential for control of vascular functions. Dysfunction of the vascular endothelium is regarded as an important factor in the pathogenesis of diabetic micro- and macro-angiopathy. Endothelial dysfunction in Type I and II diabetes complicated by micro- or macro-albuminuria is generalized in that it affects many aspects of endothelial function and occurs not only in the kidney. The close linkage between microalbuminuria and endothelial dysfunction in diabetes is an attractive explanation for the fact that microalbuminuria is a risk marker for atherothrombosis. In Type I diabetes, endothelial dysfunction precedes and may cause diabetic microangiopathy, but it is not clear whether endothelial dysfunction is a feature of the diabetic state itself. In Type II diabetes, endothelial function is impaired from the onset of the disease and is strongly related to adverse outcomes. It is not clear whether impaired endothelial function is caused by hyperglycaemia or by other factors. Impaired endothelial function is closely associated with and may contribute to insulin resistance regardless of the presence of diabetes. Endothelial dysfunction in diabetes originates from three main sources. Hyperglycaemia and its immediate biochemical sequelae directly alter endothelial function or influence endothelial cell functioning indirectly by the synthesis of growth factors, cytokines and vasoactive agents in other cells. Finally, the components of the metabolic syndrome can impair endothelial function.

Clinical studies of advanced glycation end product inhibitors and diabetic kidney disease

Current treatment of the nephropathy complication of diabetes mellitus is suboptimal in halting the progression of the complex disease. Among the irreversible effects of sustained hyperglycemia is the heightened formation of advanced glycation end products (AGEs). The role of AGEs in diabetic nephropathy has been established by years of basic research. This article reports progression through human studies of the few AGE inhibitors that have reached clinical development, including pimagedine, pyridoxamine, and alagebrium.