Early Formation of Serum Advanced Glycation End-Products in Children with Type 1 Diabetes Mellitus: Relationship with Glycemic Control

Procyanidins: A promising anti-diabetic agent with potential benefits on glucose metabolism and diabetes complications

Diabetes mellitus (DM) is a complex disease with alarming worldwide health implications and high mortality rates, largely due to its complications such as cardiovascular disease, nephropathy, neuropathy, and retinopathy. Recent research has shown that procyanidins (PC), a type of flavonoid, have strong antioxidant and free radical elimination effects, and may be useful in improving glucose metabolism, enhancing pancreatic islet cell activity, and decreasing the prevalence of DM complications. This review article presents a systematic search for peer-reviewed articles on the use of PC in the treatment of DM, without any language restrictions. The article also discusses the potential for PC to sensitise DM medications and improve their efficacy. Recent in vivo and in vitro studies have demonstrated promising results in improving the biological activity and bioavailability of PC for the treatment of DM. The article concludes by highlighting the potential for novel materials and targeted drug delivery methods to enhance the pharmacokinetics and bioactivity of PC, leading to the creation of safer and more effective anti-DM medications in the future.

Serum carboxymethyllysine concentration is associated with erosive hand osteoarthritis

OBJECTIVE

Carboxymethyllysine (CML) and homocitrulline (HCit) are the products of two non-enzymatic post-translational modifications of protein, a process related to age. We investigated whether serum CML and HCit concentrations were associated with hand osteoarthritis (HOA), especially erosive HOA.

DESIGN

Serum CML and HCit were measured by using liquid chromatography coupled with tandem mass spectrometry at inclusion in 386 patients included in the DIGICOD cohort. We investigated whether serum CML and/or HCit concentrations were associated with erosive HOA or with HOA clinical and radiological features. Moreover, we compared the tissular concentrations of CML and HCit in OA and non-OA cartilage from proximal interphalangeal and metacarpo-phalangeal (MCP) joints from human cadaveric donors.

RESULTS

Median (IQR) serum CML concentration was lower in patients with erosive HOA than those with non-erosive HOA (178.7 [157.1-208.8] vs 194.7 [168.9-217.1] μmol/mol Lys, p=0.002), but median HCit concentration did not differ between the groups (193.9 [162.9-232.0] vs 193.9 [155.9-224.6] μmol/mol Lys). Cartilage HCit and CML concentrations were not correlated with clinical features. Serum CML concentration was higher in OA than non-OA MCPs (7.0 vs 4.0 mmol/mol Lys, p=0.01).

CONCLUSIONS

Serum CML concentration was lower in erosive HOA than non-erosive HOA, and cartilage CML concentration was higher in OA than non-OA cartilage. These results encourage further studies to test whether serum CML could be a new prognostic biomarker in HOA.

HbA1c and biomarkers of diabetes mellitus in Clinical Chemistry and Laboratory Medicine: ten years after

Since its discovery in the late 1960s, HbA_1c has proven to be a major biomarker of diabetes mellitus survey and diagnosis. Other biomarkers have also been described using classical laboratory methods or more innovative, non-invasive ones. All biomarkers of diabetes, including the historical glucose assay, have well-controlled strengths and limitations, determining their indications in clinical use. They all request high quality preanalytical and analytical methodologies, necessitating a strict evaluation of their performances by external quality control assessment trials. Specific requirements are needed for point-of-care testing technologies. This general overview, which describes how old and new tools of diabetes mellitus biological survey have evolved over the last decade, has been built through the prism of papers published in Clinical Chemistry and Laboratory Medicine during this period.

Association Between the Tissue and Circulating Advanced Glycation End-Products and the Micro- and Macrovascular Complications in Type 1 Diabetes: The DIABAGE Study

INTRODUCTION

Type 1 diabetes is associated with an increased risk of vascular complications. We aimed to investigate the association between serum and tissue advanced glycation end-products (AGEs) and micro- and macrovascular complications in type 1 diabetes (T1D).

METHODS

We conducted a cross-sectional study on 196 adults with T1D (mean age 44.53 ± 16, mean duration of diabetes 22 ± 12 years, mean HbA1c 8 ± 1.2%). AGEs were measured in blood serum (i.e., carboxymethyllysine (CML), methylglyoxal-hydroimidazolone-1 (MGH1), and pentosidine) and by measurement of skin autofluorescence (SAF). Associations between AGEs levels and vascular complications were analyzed using binary logistic regression. Correlations between AGEs and pulse wave velocity (PWV) were also assessed by linear regressions. Significant differences were set for p values less than 0.05.

RESULTS

We found positive associations between different AGEs and vascular complications. SAF was associated with both microangiopathy (retinopathy: OR = 1.92, p = 0.011; neuropathy: OR = 2.02, p = 0.04; any microangiopathy: OR = 2.83, p < 0.0001) and macroangiopathy (coronaropathy: OR = 3.11, p = 0.009; any macroangiopathy: OR = 2.78, p = 0.003). For circulating AGEs, pentosidine was significantly associated with coronaropathy (OR = 1.61, p = 0.01) and any macroangiopathy (OR = 1.52, p = 0.005) while MGH1 was associated with nephropathy (OR 1.72, p = 0.03). Furthermore, a significant linear correlation was found between PWV and SAF (r = 0.43, p < 0.001), pentosidine (r = 0.28, p < 0.001), and MGH1 (r = 0.16, p = 0.031), but not for CML (r = 0.03, p = 0.598).

CONCLUSIONS

Skin autofluorescence appears to be a useful marker for investigating both micro- and macrovascular complications in T1D. In this study, pentosidine was associated with macroangiopathy and MGH1 with nephropathy among the circulating AGEs. Furthermore, the correlations between PWV and AGEs may suggest their value in early prediction of vascular complications in T1D.

Advanced Glycation End Products: New Clinical and Molecular Perspectives

Diabetes mellitus (DM) is considered one of the most massive epidemics of the twenty-first century due to its high mortality rates caused mainly due to its complications; therefore, the early identification of such complications becomes a race against time to establish a prompt diagnosis. The research of complications of DM over the years has allowed the development of numerous alternatives for diagnosis. Among these emerge the quantification of advanced glycation end products (AGEs) given their increased levels due to chronic hyperglycemia, while also being related to the induction of different stress-associated cellular responses and proinflammatory mechanisms involved in the progression of chronic complications of DM. Additionally, the investigation for more valuable and safe techniques has led to developing a newer, noninvasive, and effective tool, termed skin fluorescence (SAF). Hence, this study aimed to establish an update about the molecular mechanisms induced by AGEs during the evolution of chronic complications of DM and describe the newer measurement techniques available, highlighting SAF as a possible tool to measure the risk of developing DM chronic complications.

In depth investigation of collagen non-enzymatic glycation by Raman spectroscopy

Non-enzymatic glycation is a post-translational modification of long-lived matrix proteins such as type I collagen. It occurs during aging and leads to the formation of advanced glycation end-products (AGEs). AGE accumulation is associated with severe complications in chronic and age-related diseases. The assessment of modifications induced by this (patho)physiological process represents an interest in biology and medicine for a better patient care. The objective of our work was to position the interest of Raman spectroscopy in the quantification of collagen glycation. Two types of in vitro glycation were used by incubating collagen samples, at different durations, with ribose or glyoxylic acid; these reducing agents acting on the chemical specificity of the glycation reaction. Glycation efficiency was evaluated by the liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) quantification of carboxymethyllysine (CML) and pentosidine, which are among the most studied AGEs. Raman data were processed by PCA coupled to validity indices and Lasso regression as multivariate analysis tools. Regression models were constructed by considering the LC-MS/MS results as reference values. A marked variability was observed within the Raman datasets making difficult the identification of spectral differences between control and ribose-treated collagen samples. By taking advantage of the chemical specificity of the glyoxylic acid treatment leading to CML formation, on one hand, and the feature selection included in the Lasso algorithm, on the other hand, Raman markers associated with glycation were identified. The assigned vibrations corresponded to modifications of side chains of collagen. In addition, a threshold of CML concentration was determined as quantitative indicator of the applicability of Raman spectroscopy for potential patient follow-up purposes. Although lacking in sensitivity to directly detect AGEs in collagen, Raman spectroscopy allows to highlight the molecular modifications of collagen induced by glycation.

Comprehensive Quantification of Carboxymethyllysine-Modified Peptides in Human Plasma

A prolonged hyperglycemic condition in diabetes mellitus results in glycation of plasma proteins. N(ε)-Carboxymethyllysine (CML) is a well-known protein advanced glycation end product, and one of its mechanisms of formation is through further oxidation of Amadori compound modified lysine (AML). Unlike enrichment of AML peptides using boronate affinity, biochemical enrichment methods are scarce for comprehensive profiling of CML-modified peptides. To address this problem, we used AML peptide sequence and site of modification as template library to identify and quantify CML peptides. In this study, a parallel reaction monitoring workflow was developed to comprehensively quantify CML modified peptides in Type 1 diabetic subjects' plasma with good and poor glycemic control (n = 20 each). A total of 58 CML modified peptides were quantified, which represented 57 CML modification sites in 19 different proteins. Out of the 58 peptides, five were significantly higher in poor glycemic control samples with the area under the receiver operating characteristic curve ≥0.83. These peptides could serve as promising indicators of glycemic control in Type 1 diabetes management.

Evidence of Early Diabetic Nephropathy in Pediatric Type 1 Diabetes

BACKGROUND

Diabetic nephropathy (DN) is one of the most common microvascular complications in type 1 diabetes Mellitus (T1D). Urinary markers of renal damage or oxidative stress may signal early stages of DN. The association of these markers with blood pressure (BP) patterns and glycemic variability (GV) in children is yet to be explored.

METHODS

Subjects between the ages of 10 and 21 years with T1D were enrolled. Continuous glucose monitoring (CGM) and ambulatory blood pressure monitoring (ABPM) were performed on each subject. Urine samples were collected and analyzed for albumin, creatinine, neutrophil gelatinase-associated lipocalin (NGAL) and pentosidine.

RESULTS

The study included 21 subjects (62% female) with median age of 16.8 (IQR: 14.5, 18.9). Median HbA1C was 8.4 (IQR: 7.5, 9.3). While microalbuminuria was negative in all but one case (4.8%), urinary NGAL/Cr and pentosidine/Cr ratios were significantly elevated (P<0.001) in diabetic patients despite having normal microalbuminuria, and they correlated significantly with level of microalbumin/Cr (r=0.56 [CI: 0.17, 0.8] and r=0.79 [CI: 0.54, 0.91], respectively). Using ABPM, none had hypertension, however, poor nocturnal systolic BP dipping was found in 48% of cases (95% CI: 28-68%). Urinary NGAL/Cr negatively correlated with nocturnal SBP dipping (r=-0.47, CI: -0.76, -0.03). Urine NGAL/Cr also showed a significant negative correlation with HbA1c measurements, mean blood glucose, and high blood glucose index (r=-0.51 [CI: -0.78, -0.09], r=-0.45 [CI: -0.74, -0.03], and r=-0.51 [CI: -0.77, -0.1], respectively). Median urinary NGAL/Cr and pentosidine/Cr ratios were higher in the high GV group but were not significantly different.

DISCUSSION

This pilot study explores the role of ABPM and urinary markers of tubular health and oxidative stress in early detection of diabetic nephropathy. GV may play a role in the process of this diabetic complication.

Food Intake REstriction for Health OUtcome Support and Education (FIREHOUSE) Protocol: A Randomized Clinical Trial

Fire Department of New York (FDNY) rescue and recovery workers exposed to World Trade Center (WTC) particulates suffered loss of forced expiratory volume in 1 s (FEV1). Metabolic Syndrome increased the risk of developing WTC-lung injury (WTC-LI). We aim to attenuate the deleterious effects of WTC exposure through a dietary intervention targeting these clinically relevant disease modifiers. We hypothesize that a calorie-restricted Mediterranean dietary intervention will improve metabolic risk, subclinical indicators of cardiopulmonary disease, quality of life, and lung function in firefighters with WTC-LI. To assess our hypothesis, we developed the Food Intake REstriction for Health OUtcome Support and Education (FIREHOUSE), a randomized controlled clinical trial (RCT). Male firefighters with WTC-LI and a BMI > 27 kg/m2 will be included. We will randomize subjects (1:1) to either: (1) Low Calorie Mediterranean (LoCalMed)-an integrative multifactorial, technology-supported approach focused on behavioral modification, nutritional education that will include a self-monitored diet with feedback, physical activity recommendations, and social cognitive theory-based group counseling sessions; or (2) Usual Care. Outcomes include reduction in body mass index (BMI) (primary), improvement in FEV1, fractional exhaled nitric oxide, pulse wave velocity, lipid profiles, targeted metabolic/clinical biomarkers, and quality of life measures (secondary). By implementing a technology-supported LoCalMed diet our FIREHOUSE RCT may help further the treatment of WTC associated pulmonary disease.

Association of physical fitness with skin autofluorescence-derived advanced glycation end products in children

BACKGROUND

Advanced glycation end products (AGEs) accumulate with age and development of cardiovascular disease. Higher AGEs have been shown in children with diabetes but little is known about their association with lifestyle conditions in childhood. We hypothesized that BMI, blood pressure and cardiorespiratory fitness (CRF) are associated with subcutaneous AGEs formation in children.

METHODS

In this cross-sectional study, 1075 children (aged 7.2 ± 0.4 years) were screened for subcutaneous AGEs (skin autofluorescence; SAF), body mass index (BMI), blood pressure (BP), and CRF using standardized procedures. Group comparisons were performed in clinical BP and BMI categories and tertiles of CRF.

RESULTS

Children with higher physical fitness showed lower SAF (0.99(1.03;1.10)au) compared to children with low CRF (1.09(1.03;1.05)au, p < 0.001). An increase of one shuttle run stage was associated with a mean reduction in SAF of -0.033(CI: -0.042;-0.024)au, independent of BMI and BP (p < 0.001). BMI and BP were not independently associated with SAF-derived AGEs in this large cohort of primary school children.

CONCLUSIONS

Low physical fitness but not BMI and BP were associated with higher levels of AGEs. Primary prevention programs in young children may need to focus on improving physical fitness in game settings in order to reduce the growing prevalence of metabolic disorders during childhood.

The Effects of Synbiotic Supplementation on Glycemic Status, Lipid Profile, and Biomarkers of Oxidative Stress in Type 1 Diabetic Patients. A Placebo-Controlled, Double-Blind, Randomized Clinical Trial

BACKGROUND AND OBJECTIVE

The aim of the present study was to evaluate the effects of synbiotic on glycemic status, lipid profile, and biomarkers of oxidative stress in type 1 diabetes mellitus (T1DM) patients.

MATERIALS AND METHODS

In this double-blind clinical trial, 50 T1DM patients were randomly allocated to intervention (n = 25) and control (n = 25) groups and received either synbiotic powder (Lactobacillus sporogenes GBI-30 (probiotic), maltodextrin and fructooligosaccharide (prebiotic)) or placebo 2 g per day for 8 weeks. Fasting blood samples were collected before and after the intervention to measure fasting blood glucose (FBG), insulin concentration, hemoglobin A1c (HbA1c), lipid profile, and biomarkers of oxidative stress such as total antioxidant capacity (TAC) and hs-C-reactive protein (hs-CRP).

RESULTS

Supplementation with synbiotic resulted in a significant decrease in the mean serum levels of HbA1c and hs-CRP (p = 0.01 and p = 0.004, respectively), and marginally significant decrease in FBG (p = 0.05) in the intervention group post- intervention. Also, the mean changes of FBG and hs-CRP were significantly lower in the intervention group compared with the control group (p = 0.03 and p = 0.005, respectively). There were no significant changes found in lipid profile in intervention group post-intervention (p≥ 0.05). The mean serum levels of insulin and TAC were significantly increased in the intervention group post-intervention (p = 0.001). There was a significant increase in the mean changes of TAC (p = 0.005) in the intervention group compared with the control group.

CONCLUSION

The 8-week synbiotic supplementation in T1DM patients may be effective in improvement of FBG, HbA1c, insulin, hs-CRP, and TAC.

Towards normalization selection of Raman data in the context of protein glycation: application of validity indices to PCA processed spectra

Vibrational data of biological samples require appropriate pre-processing for ensuring relevant interpretation. Here, mathematical criteria (validity indices) are used to select how to normalize Raman data collected in the protein glycation context.

Post-translational modification-derived products are associated with frailty status in elderly subjects

Background Identifying frail elderly subjects is of paramount importance in order to conduct a tailored care. The characterization of frailty status is currently based on the collection of clinical data and on the use of various tools such as Fried's criteria, which constitutes a difficult and time-consuming process. Up to now, no biological markers have been described as reliable tools for frailty characterization. We tested the hypothesis that a link between frailty and protein molecular aging existed. This study aimed therefore at determining whether post-translational modification derived products (PTMDPs), recognized as biomarkers of protein aging, were associated with frailty status in elderly subjects. Methods Frailty status was determined according to Fried's criteria in 250 elderly patients (>65 years old) hospitalized in a short-term care unit. Serum concentrations of protein-bound PTMDPs, including carboxymethyllysine (CML), pentosidine, methylglyoxal-hydroimidazolone-1 and homocitrulline (HCit), were determined by liquid chromatography coupled with tandem mass spectrometry, and tissue content of advanced glycation end-products was assessed by skin autofluorescence (SAF) measurement. Associations between PTMDPs and frailty status were analyzed using logistic regression models. Results Frail patients had significantly (p<0.01) higher CML, HCit, and SAF values compared to non-frail and pre-frail subjects. By multivariate analysis, only HCit concentrations and SAF values remained associated with frailty status (p=0.016 and p=0.002, respectively), independently of age, comorbidities, renal function, C-reactive protein and albumin concentrations. Conclusions HCit and SAF are significantly associated with frailty status in elderly subjects. This study suggests that PTMDPs constitute promising biomarkers for identifying frail patients and guiding personalized patient care.

Cell Based Therapy for Type 1 Diabetes: Should We Take Hyperglycemia Into Account?

Diabetes mellitus is characterized by long standing hyperglycemia leading to numerous life-threatening complications. For type 1 diabetes mellitus, resulting from selective destruction of insulin producing cells by exaggerated immune reaction, the only effective therapy remains exogenous insulin administration. Despite accurate compliance to treatment of certain patients, transient episodes of hyperglycemia cannot be completely eliminated by this symptomatic treatment. Novel immunotherapeutic approaches based on tolerogenic dendritic cells, T regulatory cells and mesenchymal stem cells (MSCs) have been tested in clinical trials, endeavoring to directly modulate the autoimmune destruction process in pancreas. However, hyperglycemia itself affects the immune system and the final efficacy of cell-based immunotherapies could be affected by the different glycemic control of enrolled patients. The present review explores the impact of hyperglycemia on immune cells while providing greater insight into the molecular mechanisms of high glucose action and subsequent metabolic reprogramming of different immune cells. Furthermore, over-production of mitochondrial reactive oxygen species, formation of advanced glycation end products as a consequence of hyperglycemia and their downstream signalization in immune cells are also discussed. Since hyperglycemia in patients with type 1 diabetes mellitus might have an impact on immune-interventional treatment, the maintenance of a tight glucose control seems to be beneficial in patients considered for cell-based therapy.

Food advanced glycation end products as potential endocrine disruptors: An emerging threat to contemporary and future generation

Mankind exposure to chemicals in the past century has increased dramatically throughout environment. There is no question that chemicals interfere with the physiology of biological system. Abundance of chemicals is documented to be detrimental to human and wildlife. The mammalian endocrine system is comprised of many interacting tissues mediate themselves through hormones that are essential for metabolism, growth and development. Humans secrete over fifty different hormones to orchestrate major physiological functions however; these vital functions can be intervened by huge number of internal and external chemical stressors that are identified as endocrine disruptors. Advanced glycation end products (AGEs), familiarly known as Maillard products, formed through non-enzymatic glycation whose production is augmented on aging as well as environmental stressors. Processed foods have become very popular today due to their taste, convenience, and inexpensiveness. Manufacture of these day-to-day foods involves extreme temperatures on processing results in the formation of AGEs could independently promote oxidative stress, aging, diabetes, cancer, degenerative diseases, more fascinatingly hormonal disruption is the subject of interest of this review. Based on some substantial observations documented till time, we discuss the emergence of dietary AGEs as potential endocrine disruptors by emphasizing their occurrence, mechanisms and participation in endocrine interruption. Both economically and in terms of human life, AGEs may represent an enormous cost for the future society. Therefore, by explicating their novel role in endocrine diseases, the review strives to make an impact on AGEs and their exposure among public as well as scientific communities.

Impairment of glyoxalase-1, an advanced glycation end-product detoxifying enzyme, induced by inflammation in age-related osteoarthritis

BACKGROUND

Accumulation of advanced glycation end-products (AGEs) is involved in age-related osteoarthritis (OA). Glyoxalase (Glo)-1 is the main enzyme involved in the removal of AGE precursors, especially carboxymethyl-lysine (CML). We aimed to investigate the expression of several AGEs and Glo-1 in human OA cartilage and to study chondrocytic Glo-1 regulation by inflammation, mediated by interleukin (IL)-1β.

METHODS

Ex vivo, we quantified AGEs (pentosidine, CML, methylglyoxal-hydroimidazolone-1) in knee cartilage from 30 OA patients. Explants were also incubated with and without IL-1β, and we assessed Glo-1 protein expression and enzymatic activity. In vitro, primary cultured murine chondrocytes were stimulated with increasing concentrations of IL-1β to assess Glo-1 enzymatic activity and expression. To investigate the role of oxidative stress in the IL-1β effect, cells were also treated with inhibitors of mitochondrial oxidative stress or nitric oxide synthase.

RESULTS

Ex vivo, only the human cartilage CML content was correlated with patient age (r = 0.78, p = 0.0031). No statistically significant correlation was found between Glo-1 protein expression and enzymatic activity in human cartilage and patient age. We observed that cartilage explant stimulation with IL-1β decreased Glo-1 protein expression and enzymatic activity. In vitro, we observed a dose-dependent decrease in Glo-1 mRNA, protein quantity, and enzymatic activity in response to IL-1β in murine chondrocytes. Inhibitors of oxidative stress blunted this downregulation.

CONCLUSION

Glo-1 is impaired by inflammation mediated by IL-1β in chondrocytes through oxidative stress pathways and may explain age-dependent accumulation of the AGE CML in OA cartilage.

Maillard Proteomics: Opening New Pages

Protein glycation is a ubiquitous non-enzymatic post-translational modification, formed by reaction of protein amino and guanidino groups with carbonyl compounds, presumably reducing sugars and α-dicarbonyls. Resulting advanced glycation end products (AGEs) represent a highly heterogeneous group of compounds, deleterious in mammals due to their pro-inflammatory effect, and impact in pathogenesis of diabetes mellitus, Alzheimer's disease and ageing. The body of information on the mechanisms and pathways of AGE formation, acquired during the last decades, clearly indicates a certain site-specificity of glycation. It makes characterization of individual glycation sites a critical pre-requisite for understanding in vivo mechanisms of AGE formation and developing adequate nutritional and therapeutic approaches to reduce it in humans. In this context, proteomics is the methodology of choice to address site-specific molecular changes related to protein glycation. Therefore, here we summarize the methods of Maillard proteomics, specifically focusing on the techniques providing comprehensive structural and quantitative characterization of glycated proteome. Further, we address the novel break-through areas, recently established in the field of Maillard research, i.e., in vitro models based on synthetic peptides, site-based diagnostics of metabolism-related diseases (e.g., diabetes mellitus), proteomics of anti-glycative defense, and dynamics of plant glycated proteome during ageing and response to environmental stress.

Probing Protein Glycation by Chromatography and Mass Spectrometry: Analysis of Glycation Adducts

Glycation is a non-enzymatic post-translational modification of proteins, formed by the reaction of reducing sugars and α-dicarbonyl products of their degradation with amino and guanidino groups of proteins. Resulted early glycation products are readily involved in further transformation, yielding a heterogeneous group of advanced glycation end products (AGEs). Their formation is associated with ageing, metabolic diseases, and thermal processing of foods. Therefore, individual glycation adducts are often considered as the markers of related pathologies and food quality. In this context, their quantification in biological and food matrices is required for diagnostics and establishment of food preparation technologies. For this, exhaustive protein hydrolysis with subsequent amino acid analysis is the strategy of choice. Thereby, multi-step enzymatic digestion procedures ensure good recoveries for the most of AGEs, whereas tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode with stable isotope dilution or standard addition represents “a gold standard” for their quantification. Although the spectrum of quantitatively assessed AGE structures is continuously increases, application of untargeted profiling techniques for identification of new products is desired, especially for in vivo characterization of anti-glycative systems. Thereby, due to a high glycative potential of plant metabolites, more attention needs to be paid on plant-derived AGEs.