Dietary Glycation Products Pile Up Unevenly Across Aging Organs, Mouse Study Shows

When we grill, fry, or roast our food, a family of chemical reactions between sugars and proteins quietly manufactures compounds that many scientists have long suspected of accelerating aging. Among the most scrutinized of these are advanced glycation end products, or AGEs, a group of modified amino acids that form when reactive carbonyl compounds latch onto lysine residues in proteins. Two of the best-studied members of this family are Nε-(carboxymethyl)lysine, known as CML, and Nε-(carboxyethyl)lysine, or CEL. Both can be produced inside the body through normal metabolism, but both also arrive ready-made from the diet, raising a question that has dogged the field for decades: when we eat these compounds, where do they actually end up?

A new study from researchers at the Korea Food Research Institute, published in Food Science and Biotechnology, offers one of the most detailed answers yet for aging bodies. Led by Yu Ra Lee and corresponding author Yoonsook Kim, the team used targeted tandem mass spectrometry to track CML and CEL across five compartments in aged mice: blood plasma, kidney, liver, brain, and ileum, the final segment of the small intestine where most nutrient absorption occurs. The results reveal a strikingly uneven landscape, with dietary CML driving dramatic accumulations in some tissues while leaving others seemingly untouched, and with blood levels telling only a partial story about what is happening deep inside organs.

The experimental design was straightforward but technically demanding. Aged mice received a diet supplemented with CML, allowing the researchers to follow the fate of a single, well-defined dietary glycation product rather than the complex cocktail found in heat-processed foods. A second group received FPS-ZM1, a synthetic compound that blocks the receptor for advanced glycation end products, known as RAGE, a cell-surface protein that binds AGEs and triggers inflammatory signaling. By comparing these groups against controls, the researchers could disentangle how much of the tissue burden came from the diet itself and how blocking the AGE receptor might alter the picture.

The mass spectrometry approach deserves attention because quantifying AGEs is notoriously difficult. CML and CEL are small, chemically similar modifications of lysine, and tissues contain a bewildering array of proteins that may carry them. Targeted tandem mass spectrometry, often abbreviated LC-MS/MS when coupled to liquid chromatography, works by first separating the compounds chromatographically and then fragmenting them in the instrument, monitoring specific parent-to-fragment ion transitions that act like molecular fingerprints. This selective monitoring, typically run in multiple reaction monitoring mode, allows the method to distinguish CML from the sea of other molecules in a tissue digest and to quantify it against stable isotope-labeled internal standards, delivering accuracy that older colorimetric or antibody-based assays could not match.

What the numbers showed was remarkable. Compared with control animals, mice fed dietary CML accumulated 3.78 times more CML in their kidneys and a striking 10.26 times more in the ileum. CEL, which was not directly supplemented but can form downstream from related carbonyl chemistry, also rose significantly, increasing 2.33-fold in kidney and 1.69-fold in ileum. The ileum result is perhaps the most intuitive: as the site of absorption, the intestinal wall sees the highest concentration of anything arriving from the gut lumen, and the new data confirm that dietary CML does not simply pass through but accumulates in the tissue itself. The kidney, meanwhile, is a known hotspot for AGE deposition in aging and diabetes, and these findings reinforce its status as a primary sink for glycation products.

Just as telling were the tissues where the signal was weaker. The liver and brain did not show the same dramatic fold-changes, suggesting that tissue-selective barriers and metabolism shape the distribution of dietary AGEs. The blood-brain barrier, which tightly regulates what enters the central nervous system, may filter out a substantial share of circulating glycation products, though the receptor RAGE is known to mediate transport of certain ligands across that barrier under some conditions. The liver, as the body’s principal detoxification organ, may clear or process absorbed AGEs efficiently. Whatever the mechanisms, the study makes clear that a dietary bolus of CML does not blanket the body uniformly; it concentrates where physiology allows.

The correlation analysis added a layer of nuance with real clinical implications. Plasma CML levels correlated positively with CML levels in the brain, with a Spearman coefficient of 0.574 and a p-value of 0.002, and with the ileum, at a coefficient of 0.414 and p equal to 0.036. In other words, a blood draw gave a statistically meaningful window into glycation burden in at least two organs. But plasma CEL told a different story entirely, showing no significant correlations with any tissue measured. For researchers and clinicians who rely on circulating AGE markers as proxies for whole-body or organ-specific burden, this is a caution: the reliability of a blood marker depends on which AGE you are measuring and which tissue you care about.

The FPS-ZM1 arm of the experiment pointed toward a possible intervention strategy. Mice that received the RAGE antagonist showed lower AGE levels in selected tissues compared with animals that did not. RAGE is not merely a passive binding protein; when engaged by AGEs, it activates inflammatory and oxidative stress pathways that have been implicated in diabetic complications, kidney disease, cardiovascular damage, and neurodegeneration. Blocking the receptor has previously been shown in other mouse models to reduce amyloid-beta-related brain pathology, and the new findings suggest that RAGE signaling may also influence how glycation products distribute and persist in aging tissue. The authors describe the association carefully, and the study was not designed as a therapeutic trial, but the pattern supports the idea that the AGE-RAGE axis is a meaningful lever in age-related tissue accumulation.

Why does this matter for human health? The modern Western diet, rich in heat-processed and industrially prepared foods, delivers a substantial daily load of preformed AGEs, and epidemiological and mechanistic studies have linked high dietary AGE intake to obesity, early renal pathology, and chronic inflammation. Prior work with isotopically labeled dietary CML in mice demonstrated that a fraction of orally administered CML is absorbed and distributed to organs, but questions remained about how aging changes that distribution and whether blood measurements could stand in for tissue measurements. The new study addresses both gaps in aged animals, showing that the aging kidney and gut are particularly receptive to dietary CML and that plasma markers must be interpreted with tissue context in mind.

There are, of course, limits to how far mouse data can be extrapolated. The study used a purified CML supplement rather than the heterogeneous AGE mixture found in actual foods, and the doses, metabolism, and lifespan of laboratory mice differ from those of humans. The researchers also note that endogenous AGE formation, driven by oxidative stress and reactive carbonyls such as methylglyoxal and glyoxal, proceeds alongside dietary intake and can complicate attribution. Still, by applying a rigorously validated targeted mass spectrometry method across five biological compartments in aged animals, the Korean team has produced a map of where dietary glycation products actually go, and that map argues for caution in reading blood tests, continued scrutiny of AGE-rich diets, and sustained interest in RAGE as a target for protecting aging organs from the slow chemical wear of glycation.

Subject of Research: Tissue-selective accumulation of dietary advanced glycation end products in aged mice

Article Title: Tissue-selective accumulation of carboxymethyllysine and carboxyethyllysine after dietary carboxymethyllysine exposure in aged mice revealed by targeted tandem mass spectrometry

Article References: Tissue-selective accumulation of carboxymethyllysine and carboxyethyllysine after dietary carboxymethyllysine exposure in aged mice revealed by targeted tandem mass spectrometry. (n.d.). https://doi.org/10.1007/s10068-026-02332-4

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02332-4

Keywords: advanced glycation end products, carboxymethyllysine, carboxyethyllysine, tandem mass spectrometry, aging, kidney, ileum, RAGE, dietary AGEs, plasma biomarkers, glycation, mice study