A Citrus and Pomegranate Complex Reduces Methylglyoxal in Healthy Elderly Subjects: Secondary Analysis of a Double-Blind Randomized Cross-Over Clinical Trial.

Reactive α-dicarbonyls (α-DCs), such as methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG), are potent precursors in the formation of advanced glycation end products (AGEs). In particular, MGO and MGO-derived AGEs are thought to be involved in the development of vascular complications in diabetes. Experimental studies showed that citrus and pomegranate polyphenols can scavenge α-DCs. Therefore, the aim of this study was to evaluate the effect of a citrus and pomegranate complex (CPC) on the α-DCs plasma levels in a double-blind, placebo-controlled cross-over trial, where thirty-six elderly subjects were enrolled. They received either 500 mg of Citrus sinensis peel extract and 200 mg of Punica granatum concentrate in CPC capsules or placebo capsules for 4 weeks, with a 4-week washout period in between. For the determination of α-DCs concentrations, liquid chromatography tandem mass spectrometry was used. Following four weeks of CPC supplementation, plasma levels of MGO decreased by 9.8% (-18.7 nmol/L; 95% CI: -36.7, -0.7 nmol/L; p = 0.042). Our findings suggest that CPC supplementation may represent a promising strategy for mitigating the conditions associated with MGO involvement. This study was registered on clinicaltrials.gov as NCT03781999.

Higher Plasma Methylglyoxal Levels Are Associated With Incident Cardiovascular Disease and Mortality in Individuals With Type 2 Diabetes.

OBJECTIVE: Methylglyoxal (MGO) is a reactive dicarbonyl compound and a potential key player in diabetic cardiovascular disease (CVD). Whether plasma MGO levels are associated with CVD in type 2 diabetes is unknown. RESEARCH DESIGN AND METHODS: We included 1,003 individuals (mean ± SD age 59.1 ± 10.5 years, 69.3% male, and 61.6% with prior CVD) with type 2 diabetes from the Second Manifestations of ARTerial disease cohort (SMART). We measured plasma MGO levels and two other dicarbonyls (glyoxal [GO] and 3-deoxyglucosone [3-DG]) at baseline with mass spectrometry. Median follow-up of CVD events was 8.6 years. Data were analyzed with Cox regression with adjustment for sex, age, smoking, systolic blood pressure, total cholesterol, HbA1c, BMI, prior CVD, and medication use. Hazard ratios are expressed per SD Ln-transformed dicarbonyl. RESULTS: A total of 287 individuals suffered from at least one CVD event (n = 194 fatal events, n = 146 myocardial infarctions, and n = 72 strokes); 346 individuals died, and 60 individuals underwent an amputation. Higher MGO levels were associated with total (hazard ratio 1.26 [95% CI 1.11-1.42]) and fatal (1.49 [1.30-1.71]) CVD and with all-cause mortality (1.25 [1.11-1.40]), myocardial infarction (1.22 [1.02-1.45]), and amputations (1.36 [1.05-1.76]). MGO levels were not apparently associated with stroke (1.03 [0.79-1.35]). Higher GO levels were significantly associated with fatal CVD (1.17 [1.00-1.37]) but not with other outcomes. 3-DG was not significantly associated with any of the outcomes. CONCLUSIONS: Plasma MGO and GO levels are associated with cardiovascular mortality in individuals with type 2 diabetes. Influencing dicaronyl levels may therefore be a target to reduce CVD in type 2 diabetes.

Dietary intake of advanced glycation endproducts is associated with higher levels of advanced glycation endproducts in plasma and urine: The CODAM study.

BACKGROUND & AIMS: Advanced glycation endproducts (AGEs) are formed by the reaction between reducing sugars and proteins. AGEs in the body have been associated with several age-related diseases. High-heat treated and most processed foods are rich in AGEs. The aim of our study was to investigate whether dietary AGEs, are associated with plasma and urinary AGE levels. METHODS: In 450 participants of the Cohort on Diabetes and Atherosclerosis Maastricht study (CODAM study) we measured plasma and urine concentrations of the AGEs Nε-(carboxymethyl)lysine (CML), Nε-(1-carboxyethyl)lysine (CEL) and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) using UPLC-MS/MS. We also estimated dietary intake of CML, CEL and MG-H1 with the use of a dietary AGE database and a food frequency questionnaire (FFQ). We used linear regression to investigate the association between standardized dietary AGE intake and standardized plasma or urinary AGE levels, after adjustment for age, sex, glucose metabolism status, waist circumference, kidney function, energy- and macro-nutrient intake, smoking status, physical activity, alcohol intake, LDL-cholesterol and markers of oxidative stress. RESULTS: We found that higher intake of dietary CML, CEL and MG-H1 was associated with significantly higher levels of free plasma and urinary CML, CEL and MG-H1 (ßCML = 0.253 (95% CI 0.086; 0.415), ßCEL = 0.194 (95% CI 0.040; 0.339), ßMG-H1 = 0.223 (95% CI 0.069; 0.373) for plasma and ßCML = 0.223 (95% CI 0.049; 0.393), ßCEL = 0.180 (95% CI 0.019; 0.332), ßMG-H1 = 0.196 (95% CI 0.037; 0.349) for urine, respectively). In addition, we observed non-significant associations of dietary AGEs with their corresponding protein bound plasma AGEs. CONCLUSION: We demonstrate that higher intake of dietary AGEs is associated with higher levels of AGEs in plasma and urine. Our findings may have important implications for those who ingest a diet rich in AGEs.

Higher Plasma Methylglyoxal Levels Are Associated With Incident Cardiovascular Disease in Individuals With Type 1 Diabetes: A 12-Year Follow-up Study.

Methylglyoxal (MGO), a major precursor for advanced glycation end products, is increased in diabetes. In diabetic rodents, inhibition of MGO prevents cardiovascular disease (CVD). Whether plasma MGO levels are associated with incident CVD in people with type 1 diabetes is unknown. We included 159 individuals with persistent normoalbuminuria and 162 individuals with diabetic nephropathy (DN) from the outpatient clinic at Steno Diabetes Center. We measured MGO at baseline and recorded fatal and nonfatal CVD over a median follow-up of 12.3 years (interquartile range 7.6-12.5 years). Data were analyzed by Cox regression, with adjustment for sex, age, HbA1c, DN, diabetes duration, smoking, systolic blood pressure, antihypertensive medication, and BMI. During follow-up, 73 individuals suffered at least one CVD event (36 fatal and 53 nonfatal). Higher MGO levels were associated with total, fatal, and nonfatal incident CVD (hazard ratios [HRs] 1.47 [95% CI 1.13-1.91], 1.42 [1.01-1.99], and 1.46 [1.08-1.98], respectively). We observed a similar trend for total mortality (HR 1.24 [0.99-1.56]). This study shows for the first time in our knowledge that plasma MGO levels are associated with cardiovascular events in individuals with type 1 diabetes. MGO may explain, at least in part, the increased risk for CVD in type 1 diabetes.

Low 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 levels are independently associated with macroalbuminuria, but not with retinopathy and macrovascular disease in type 1 diabetes: the EURODIAB prospective complications study.

BACKGROUND: Low circulating levels of total vitamin D [25(OH)D] and 25(OH)D3 have been associated with vascular complications in few studies on individuals with type 1 diabetes. However, these measures are affected by UV light exposure. Circulating 25(OH)D2, however, solely represents dietary intake of vitamin D2, but its association with complications of diabetes is currently unknown. We investigated the associations between 25(OH)D2 and 25(OH)D3 and the prevalence of albuminuria, retinopathy and cardiovascular disease (CVD) in individuals with type 1 diabetes. METHODS: We measured circulating 25(OH)D2 and 25(OH)D3 in 532 individuals (40 ± 10 years old, 51 % men) with type 1 diabetes who participated in the EURODIAB Prospective Complications Study. Cross-sectional associations of 25(OH)D2 and 25(OH)D3 with albuminuria, retinopathy and CVD were assessed with multiple logistic regression analyses adjusted for age, sex, season, BMI, smoking, HbA1c, total-HDL-cholesterol-ratio, systolic blood pressure, antihypertensive medication, eGFR, physical activity, alcohol intake, albuminuria, retinopathy and CVD, as appropriate. RESULTS: Fully adjusted models revealed that 1 nmol/L higher 25(OH)D2 and 10 nmol/L higher 25(OH)D3 were associated with lower prevalence of macroalbuminuria with ORs (95 % CI) of 0.56 (0.43;0.74) and 0.82 (0.72;0.94), respectively. These vitamin D species were not independently associated with microalbuminuria, non-proliferative and proliferative retinopathy or CVD. CONCLUSIONS: In individuals with type 1 diabetes, both higher 25(OH)D2 and 25(OH)D3 are associated with a lower prevalence of macroalbuminuria, but not of retinopathy and CVD. Prospective studies are needed to further examine the associations between 25(OH)D2 and 25(OH)D3 and the development of microvascular complications and CVD in type 1 diabetes.

Plasma advanced glycation end products are associated with incident cardiovascular events in individuals with type 2 diabetes: a case-cohort study with a median follow-up of 10 years (EPIC-NL).

Experimental data suggest a role for advanced glycation end products (AGEs) in cardiovascular disease (CVD), particularly in type 2 diabetes (T2DM). However, epidemiological evidence of an association between high plasma AGEs and increased cardiovascular risk remains inconclusive. Therefore, in a case-cohort study comprising 134 cardiovascular case subjects and a random subcohort of 218 individuals (including 65 cardiovascular case subjects), all with T2DM and nested in the European Prospective Investigation into Cancer and Nutrition in the Netherlands (EPIC-NL) study, plasma levels of protein-bound Nε-(carboxymethyl)lysine, Nε-(carboxyethyl)lysine, and pentosidine were measured with liquid chromatography. AGEs were loge-transformed, combined in a z-score, and the association with incident cardiovascular events was analyzed with Cox proportional hazard regression, adapted for case-cohort design (Prentice method). After multivariable adjustment (sex, age, cohort status, diabetes duration, total cholesterol to HDL-cholesterol ratio, smoking, systolic blood pressure, BMI, blood pressure-, cholesterol- and glucose-lowering treatment, prior cardiovascular events, and triglycerides), higher plasma AGE z-scores were associated with higher risk of incident cardiovascular events in individuals without prior cardiovascular events (hazard ratio 1.31 [95% CI: 1.06-1.61]). A similar trend was observed in individuals with prior cardiovascular events (1.37 [0.63-2.98]). In conclusion, high plasma AGEs were associated with incident cardiovascular events in individuals with T2DM. These results underline the potential importance of AGEs in development of CVD.

Higher levels of advanced glycation endproducts in human carotid atherosclerotic plaques are associated with a rupture-prone phenotype.

AIMS: Rupture-prone atherosclerotic plaques are characterized by inflammation and a large necrotic core. Inflammation is linked to high metabolic activity. Advanced glycation endproducts (AGEs) and their major precursor methylglyoxal are formed during high metabolic activity and can have detrimental effects on cellular function and may induce cell death. Therefore, we investigated whether plaque AGEs are increased in human carotid rupture-prone plaques and are associated with plaque inflammation and necrotic core formation. METHODS AND RESULTS: The protein-bound major methylglyoxal-derived AGE 5-hydro-5-methylimidazolone (MG-H1) and N(ε)-(carboxymethyl)lysine (CML) were measured in human carotid endarterectomy specimens (n = 75) with tandem mass spectrometry. MG-H1 and CML levels were associated with rupture-prone plaques, increased protein levels of the inflammatory mediators IL-8 and MCP-1 and with higher MMP-9 activity. Immunohistochemistry showed that AGEs accumulated predominantly in macrophages surrounding the necrotic core and co-localized with cleaved caspase-3. Intra-plaque comparison revealed that glyoxalase-1 (GLO-1), the major methylglyoxal-detoxifying enzyme, mRNA was decreased (-13%, P < 0.05) in ruptured compared with stable plaque segments. In line, in U937 monoctyes, we found reduced (GLO-1) activity (-38%, P < 0.05) and increased MGO (346%, P < 0.05) production after stimulation with the inflammatory mediator TNF. Direct incubation with methylglyoxal increased apoptosis up to two-fold. CONCLUSION: This is the first study showing that AGEs are associated with human rupture-prone plaques. Furthermore, this study suggests a cascade linking inflammation, reduced GLO-1, methylglyoxal- and AGE-accumulation, and subsequent apoptosis. Thereby, AGEs may act as mediators of the progression of stable to rupture-prone plaques, opening a window towards novel treatments and biomarkers to treat cardiovascular diseases.

Plasma advanced glycation end-products and skin autofluorescence are increased in COPD.

Chronic obstructive pulmonary disease (COPD) is associated with systemic inflammation and oxidative stress. These conditions may lead to the formation of advanced glycation end-products (AGEs). In this study we investigated in 88 COPD patients and 55 control subjects (80% ex-smokers) the association of the plasma protein-bound AGEs N(ε)-(carboxymethyl)lysine (CML), pentosidine, N(ε)-(carboxyethyl)lysine (CEL), and AGE accumulation in skin by skin autofluorescence (AFR), with lung function. Mean ± sd plasma CML was decreased (COPD 61.6 ± 15.6 nmol · mmol(-1) lysine, never-smokers 80.7 ± 19.8 nmol · mmol(-1) lysine and ex-smokers 82.9 ± 19.3 nmol · mmol(-1) lysine) and CEL (COPD 39.1 ± 10.9 nmol · mmol(-1) lysine, never-smokers 30.4 ± 5.0 nmol · mmol(-1) lysine and ex-smokers 27.7 ± 6.4 nmol · mmol(-1) lysine) and AFR (COPD 3.33 ± 0.67 arbitrary units (AU), never-smokers 2.24 ± 0.45 AU and ex-smokers 2.31 ± 0.47 AU) were increased in COPD patients compared to controls. Disease state was inversely associated with CML, and linearly associated with CEL and AFR. Performing regression analyses in the total group, CEL and AFR showed a negative association and CML a positive association with lung function, even after correction for potential confounders. In conclusion, CEL and AFR were negatively and CML was positively associated with disease state. In the total group only the AGEs showed an association with forced expiratory volume in 1 s. Our data suggest that AGEs are involved in the pathophysiology of COPD, although their exact role remains to be determined.

Plasma levels of advanced glycation endproducts are associated with type 1 diabetes and coronary artery calcification.

BACKGROUND: Advanced glycation endproducts (AGEs) may play a role in the development of coronary artery calcification (CAC) in type 1 diabetes (T1DM). We studied plasma AGEs in association with T1DM and CAC, and whether or not the latter association could be explained by low-grade inflammation (LGI) or endothelial dysfunction (ED). METHODS: We studied 165 individuals with and 169 without T1DM. CAC was quantified in a CAC score based on CT-scanning. Plasma levels of protein-bound pentosidine, Nϵ-(carboxymethyl)lysine (CML) and Nϵ-(carboxyethyl)lysine (CEL) were measured with HPLC/UPLC with fluorescence detection or tandem-mass spectrometry. Tetrahydropyrimidine (THP) was measured with ELISA, as were HsCRP, and sVCAM-1 and vWF, as markers for LGI and ED, respectively. Associations were analyzed with ANCOVA and adjusted for age, sex, BMI, waist-to-hip ratio, smoking, blood pressure, lipid profile, eGFR and T1DM. RESULTS: Individuals with T1DM had higher plasma levels of pentosidine, CML and THP compared with controls; means (95% CI) were 0.69 (0.65-0.73) vs. 0.51 (0.48-0.54) nmol/mmol LYS, p < 0.001; 105 (102-107) vs. 93 (90-95) nmol/mmol LYS, p < 0.001; and 126 (118-134) vs. 113 (106-120) U/mL, p = 0.03, respectively. Levels of pentosidine were higher in individuals with T1DM with a moderate to high compared with a low CAC score, means (95% CI) were 0.81 (0.70-0.93) vs. 0.67 (0.63-0.71) nmol/mmol LYS, p = 0.03, respectively. This difference was not attenuated by adjustment for LGI or ED. CONCLUSIONS: We found a positive association between pentosidine and CAC in T1DM. These results may indicate that AGEs are possibly involved in the development of CAC in individuals with T1DM.