Methylglyoxal Adducts Are Prognostic Biomarkers for Diabetic Kidney Disease in Patients With Type 1 Diabetes

Dose-Dependent Scavenging of Methylglyoxal by Naringenin in Diabetic Mice

Methylglyoxal (MGO) has driven interest as a major precursor of advanced glycation end products due to it being closely implicated in the pathogenesis of diabetic kidney disease (DKD). Therefore, it is critical for seeking active scavenger-targeted MGO to mitigate the development of DKD. Previous studies demonstrated that naringenin (Nar) has a remarkable therapeutic effect on DKD. However, whether Nar could scavenge MGO in diabetic mice remains virtually unknown. This work aims to investigate the effect and mechanism of scavenging MGO by Nar in diabetic mice. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was applied for investigating the scavenging capacity and mechanism of Nar on MGO in diabetic mice. The results indicated that Nar could significantly scavenge MGO in diabetic mice based on the formation of mono-MGO-Nar. In addition, two mono-MGO-Nar nanoparticles were purified, and their structures were deduced as 3-MGO-Nar using LC-MS/MS and NMR spectroscopic analyses. Furthermore, the dose-dependent scavenge effect of Nar on MGO in diabetic mice was elucidated by quantifying mono-MGO-Nar in urine and feces using LC-MS/MS. In summary, our results first demonstrated that targeting the MGO burden may be the new mechanism of Nar combating DKD.

Glycation metabolites predict incident age-related comorbidities and mortality in older people with HIV

Glycation is a class of modifications arising from non-enzymatic reactions of reducing sugars with proteins, lipids, and/or DNA, generating advanced glycation end-products (AGEs). AGEs are linked to many age-related comorbidities. In response to HIV-1 infection, activated T-cells and macrophages shift their predominate metabolism from oxidative phosphorylation to glycolysis. Increased glycolytic flux enhances AGE formation, which may increase age-related comorbidities. In this prospective, multicenter cohort study of antiretroviral therapy treated people with HIV, we explored predictive associations by baseline plasma AGE concentrations and their corresponding detoxification metabolites, with incident comorbidities and mortality. AGEs included dicarbonyl sugars: 3-deoxyglucosone, glyoxal, and methylglyoxal. Methylglyoxal-derived metabolites included carboxyethyl-arginine, carboxyethyl-lysine, and methylglyoxal hydroimidazolone-1. Detoxification metabolites included reduced and oxidized glutathione, and the glyoxalase cycle products lactoyl-glutathione and lactoyl-Lysine modified proteins. Plasma was collected at study entry, in the fasting state, and assayed by liquid chromatography-mass spectroscopy. Incident clinical outcomes included diabetes, chronic kidney disease, hypertension, neurocognitive impairment, peripheral neuropathy, frailty, fractures, recurrent falls, and all-cause mortality. Among 376 participants, higher baseline plasma concentrations of methylglyoxal derived AGEs predicted increased risks of diabetes, chronic kidney disease, and recurrent falls, while higher 3-deoxyglucosone predicted an increased risk of peripheral neuropathy. By contrast, higher baseline concentrations of reduced or oxidized glutathione, lactoyl-glutathione, and/or lactoyl-Lysine modified proteins predicted lower risks of diabetes, neurocognitive impairment, frailty, fractures, recurrent falls, and all-cause mortality. These findings support growing experimental evidence of the potential to mitigate age-related declines by interventions that reduce glycation or increase glutathione.

Relationship between advanced glycation end-products and advanced oxidation protein products in patients with type 2 diabetes with and without albuminuria: A cross-sectional survey

Background and Aims

Literature suggests that oxidative stress plays a crucial role in the progression of diabetes. Since poor glycemic control enhances the formation of advanced glycation end-products (AGEs) and advanced oxidation protein products (AOPP) in individuals with diabetes, exploring the association between glycation and oxidative states in diabetes could also shed light on potential consequences. This study evaluated the effects of albuminuria on AGEs and AOPP levels and measured their relationship in participants with type 2 diabetes (T2D) with or without albuminuria.

Methods

A cross-sectional, matched case-control study was designed, including 38 T2D subjects with albuminuria and 38 matched T2D subjects with normoalbuminuria. Patients were matched by their body mass index (BMI), age, and duration of diabetes. The unadjusted and adjusted correlation between AGEs and AOPP in the studied groups were analyzed by multiple logistic regression. Using ggplot2, the ties between these two biochemical factors in cases and controls were plotted.

Results

This study elucidated a significant association between AGEs and AOPP in participants with normoalbuminuria (r = 0.331, p-value < 0.05), which continued to be significant after controlling for BMI, age, systolic blood pressure (SBP), and diastolic blood pressure (DBP) (r = 0.355, p-value < 0.05). However, there was no significant association between AGEs and AOPP in those with albuminuria in the unadjusted model (r = 0.034, p-value = 0.841) or after controlling for BMI, age, SBP, and DBP (r = 0.076, p-value = 0.685).

Conclusion

Oxidation and glycation molecular biomarkers were correlated in patients without albuminuria; however, this association was not observed in those with albuminuria.

Recent advances in the potential of Phyllanthus emblica L. and its related foods for combating metabolic diseases through methylglyoxal trapping

Methylglyoxal (MG) serves as the primary precursor for the nonenzymatic glycation of proteins and DNA, leading to advanced glycation end products (AGEs). Regular intake of dietary MG is strongly correlated with low-grade inflammation, potentially accelerating the pathogenesis of metabolic diseases, including obesity, diabetes, cancers, liver diseases, Alzheimer's disease, cardiovascular diseases, aging, and bone loss. Although pharmaceutical agents (pimagedine and candesartan) have been developed to inhibit MG formation, they often come with serious side effects (nausea, diarrhea, headache, gastrointestinal disturbance, symptomatic hypotension, abnormal renal and liver function tests, development of antinuclear antibody, pernicious-like anemia, and hyperkalemia), highlighting the need for an efficient and safe approach to scavenging MG. Phyllanthus emblica Linn fruit, a nutritious edible fruit, and medicinal plant contains over 300 bioactive compounds. Among twenty-three herbals, 100 μg/mL of the aqueous extract of Phyllanthus emblica fruit (APF) exhibits the highest potency in trapping MG, achieving an 87.3 % reduction under d-fructose induced BSA-AGEs formation. However, there are few reports detailing APF and its related foods' specific impact on disease prevention through MG trapping. This review summarizes the mechanisms through which MG is linked to the development of metabolic diseases and provides several strategies for reducing MG levels using APF and its bioactive compounds. The potential antiglycation properties of APF may offer new applications in the food industry and pharmacological research.

Methylglyoxal-Derived Nucleoside Adducts Drive Vascular Dysfunction in a RAGE-Dependent Manner

Diabetic kidney disease (DKD) is a leading cause of death in patients with diabetes. An early precursor to DKD is endothelial cell dysfunction (ECD), which often precedes and exacerbates vascular disease progression. We previously discovered that covalent adducts formed on DNA, RNA, and proteins by the reactive metabolic by-product methylglyoxal (MG) predict DKD risk in patients with type 1 diabetes up to 16 years pre-diagnosis. However, the mechanisms by which MG adducts contribute to vascular disease onset and progression remain unclear. Here, we report that the most predominant MG-induced nucleoside adducts, N2-(1-carboxyethyl)-deoxyguanosine (CEdG) and N2-(1-carboxyethyl)-guanosine (CEG), drive endothelial dysfunction. Following CEdG or CEG exposure, primary human umbilical vein endothelial cells (HUVECs) undergo endothelial dysfunction, resulting in enhanced monocyte adhesion, increased reactive oxygen species production, endothelial permeability, impaired endothelial homeostasis, and exhibit a dysfunctional transcriptomic signature. These effects were discovered to be mediated through the receptor for advanced glycation end products (RAGE), as an inhibitor for intracellular RAGE signaling diminished these dysfunctional phenotypes. Therefore, we found that not only are MG adducts biomarkers for DKD, but that they may also have a role as potential drivers of vascular disease onset and progression and a new therapeutic modality.