Dietary intake associated with serum versus urinary carboxymethyl-lysine, a major advanced glycation end product, in adults: the Energetics Study

Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
European journal of clinical nutrition (Impact Factor: 2.71). 07/2011; 66(1):3-9. DOI: 10.1038/ejcn.2011.139
Source: PubMed


Advanced glycation end products (AGEs) are implicated in the pathogenesis of atherosclerosis, diabetes and kidney disease. The objective was to describe dietary intake, the dominant source of exposure to AGEs, with carboxymethyl-lysine (CML), a major AGE, in serum and urine, respectively.
Serum and urinary CML were measured in 261 adults, aged 21-69 years, and compared with diet as assessed by six separate 24-h dietary recalls.
Median (25th, 75th percentile) serum and urinary CML concentrations were 686 (598, 803) μg/l and 1023 (812, 1238) μg/gm creatinine. There was no correlation between serum and urinary CML (r=-0.02, P=0.78). Serum CML was positively correlated with intake of soy, fruit juice, cold breakfast cereal, non-fat milk, whole grains, fruit, non-starchy vegetables and legumes, and negatively correlated with intake of red meat. Intake of fast food was not significantly correlated with serum CML. Urinary CML was positively correlated with intake of starchy vegetables, whole grains, sweets, nuts/seeds and chicken, and negatively correlated with intake of fast foods. Intake of AGE-rich foods such as fried chicken, French fries, bacon/sausage and crispy snacks were not significantly correlated with serum or urinary CML, except for a significant negative correlation between fried chicken and serum CML.
These findings suggest that the high consumption of foods considered high in CML is not a major determinant of either serum or urinary CML. Further work is needed to understand the relationship of AGEs in blood and urine with the metabolism of dietary AGEs.

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    • "Some studies have demonstrated that AGE-rich diets can lead to AGEs deposition in vivo after gastrointestinal absorption or absorption through the circulatory system [7], [8]. However, other studies have shown that exogenous AGEs are not absorbed by the gastrointestinal tract and are not toxic to human health [9], [10], [11]. These findings indicate that the different biodistributions of AGEs may be related to the different functional effects of AGEs [10], [12]. "
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    ABSTRACT: N(ε)-carboxymethyl-lysine (CML) is a major advanced glycation end-product (AGEs) widely found in foods. The aim of our study was to evaluate how exogenous CML-peptide is dynamically absorbed from the gastrointestinal tract and eliminated by renal tubular secretion using microPET imaging. The present study consisted of three investigations. In study I, we synthesized the imaging tracer (18)F-CML by reacting N-succinimidyl 4-(18)F-fluorobenzoate ((18)F-SFB) with CML. In study II, the biological activity of (18)F-CML was evaluated in RAW264.7 cells and HepG2 cells. In study III, the biodistribution and elimination of AGEs in ICR mice were studied in vivo following tail vein injection and intragastric administration of (18)F-CML. The formation of (18)F-CML was confirmed by comparing its retention time with the corresponding reference compound (19)F-CML. The radiochemical purity (RCP) of (18)F-CML was >95%, and it showed a stable character in vitro and in vivo. Uptake of (18)F-CML by RAW264.7 cells and HepG2 cells could be inhibited by unmodified CML. (18)F-CML was quickly distributed via the blood, and it was rapidly excreted through the kidneys 20 min after tail vein injection. However, (18)F-CML was only slightly absorbed following intragastric administration. After administration of (18)F-CML via a stomach tube, the radioactivity was completely localized in the stomach for the first 15 min. At 150 min post intragastric administration, intense accumulation of radioactivity in the intestines was still observed. PET technology is a powerful tool for the in vivo analysis of the gastrointestinal absorption of orally administered drugs. (18)F-CML is hardly absorbed by the gastrointestinal tract. It is rapidly distributed and eliminated from blood following intravenous administration. Thus, it may not be harmful to healthy bodies. Our study showed the feasibility of noninvasively imaging (18)F-labeled AGEs and was the first to describe CML-peptide gastrointestinal absorption by means of PET.
    PLoS ONE 03/2013; 8(3):e57897. DOI:10.1371/journal.pone.0057897 · 3.23 Impact Factor
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    • "Serum CML concentrations show a moderate correlation with dietary intake of AGEs in older adults [39]. Serum CML concentrations have been reported to vary with dietary intake of AGEs [40], but these findings have not been corroborated by others [41, 42]. "
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    ABSTRACT: Advanced glycation end products (AGEs) have been implicated in the pathogenesis of sarcopenia. Our aim was to characterize the relationship between serum carboxymethyl-lysine (CML), a major circulating AGE, and incident severe walking disability (inability to walk or walking speed <0.4 m/sec) over 30 months of followup in 394 moderately to severely disabled women, ≥65 years, living in the community in Baltimore, Maryland (the Women's Health and Aging Study I). During followup, 154 (26.4%) women developed severe walking disability, and 23 women died. Women in the highest quartile of serum CML had increased risk of developing of severe walking disability in a multivariate Cox proportional hazards model, adjusting for age and other potential confounders. Women with elevated serum CML are at an increased risk of developing severe walking disability. AGEs are a potentially modifiable risk factor. Further work is needed to establish a causal relationship between AGEs and walking disability.
    Journal of aging research 08/2012; 2012(10):586385. DOI:10.1155/2012/586385
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    ABSTRACT: Background/aims: Excretion of urinary compounds in spot urine is often estimated relative to creatinine. For the growing number of liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays of urine-excreted molecules, a fast and accurate method for determination of creatinine is needed. Methods: A high-throughput flow injection tandem mass spectrometry method for exact quantitation of creatinine in urine has been developed and validated. Sample preparation used only two-step dilution for protein precipitation and matrix dilution. Flow injection analysis without chromatographic separation allowed for total run times of 1 min per sample. Creatinine concentrations were quantitated using stable isotope dilution tandem mass spectrometry. Selectivity and coelution-free quantitation were assured by qualifier ion monitoring. Results: Method validation revealed excellent injection repeatability of 1.0% coefficient of variation (CV), intraday precision of 1.2% CV and interday precision of 2.4% CV. Accuracy determined from standard addition experiments was 106.1 ± 3.8%. The linear calibration range was adapted to physiological creatinine concentrations. Comparison of quantitation results with a routinely used method (Jaffé colorimetric assay) proved high agreement (R(2) = 0.9102). Conclusions: The new method is a valuable addition to the toolbox of LC-MS/MS laboratories where excretion of urinary compounds is studied. The 'dilute and shoot' approach to isotope dilution tandem mass spectrometry makes the new method highly accurate as well as cost- and time-efficient.
    Annals of Nutrition and Metabolism 12/2012; 61(4):314-21. DOI:10.1159/000342774 · 2.62 Impact Factor
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