Pentosidine

Several markers for the Maillard reaction have been described in the literature. For example, the product initially formed between glucose and lysine is partly transformed into furosine (Heyns et ah, 1968) on acid hydrolysis. Conversely, the fluorescent amino acid pentosidine (Sell and Monnier, 1989) is an advanced glycation endproduct (AGE) and may form covalent bonds between proteins (cross-linking). Furthermore, the Maillard reaction leads to an increase in characteristic fluorescence (excitation 370 nm, emission 440 nm) (Monnier et ah, 1984 Pongor et ah, 1984). 

Materials. All reagents were analytical grade. Solutions were prepared in demineralized water. Central incisors were extracted from lower jaws of four-year old cows obtained from a local slaughterhouse. Pentosidine was a kind gift from Prof. V. Monnier, Case Western Reserve University, Cleveland OH, USA. Furosine was from Neosystem, Strasbourg, France, and hydroxylysylpyridinoline and lysylpyridinoline from Metra Biosystems, Palo Alto CA, USA. 

HPLC. Furosine and pentosidine, indicators of the initial and advanced stages of fhe Maillard reaction, respectively, increased in glucose-exposed slices (figs. 3,4 fable 3). Hydroxylysylpyridinoline apparenfly did nof form in fhe demineralized dentin at 37°C, as it did not increase in dentin exposed at 37°C (table 3). 

Furosine and fluorescent cross-links (mol amino acid/ mol collagen, except pentosidine mmol/mol) determined by HPLC in hydrolyzates of dentin slices exposed to glucose and buffer, pH 7.4, and non-exposed controls (n=2). 

Monnier VM and Sell DR (1994) The advanced Maillard reaction in aging and age-related diseases probed with pentosidine. Spec Publ - R Soc Chem 151, 235-243. 

The 328/378- and 370/440 fluorescences are characteristic for pentosidine and Maillard products, respectively (Dyer et al., 1991b) while the 317/407 fluorescence indicates dityrosine formation (Huggins et al., 1993). 

Emission spectra of blank (buffer, A), standards (D, 0.28 pM dityrosine at 317 nm P, 3.3 nM pentosidine at A,. 328 nm), digested sound dentin (B), and carious dentin (C) of a tooth from series 1. Note the increase of fluorescence in carious dentin (4-j. 

The increase of carboxymethyllysine (batch 1) and pentosidine (batches 1 and 11) thus observed provided additional proof for fhe Maillard reaction in caries (fable 3, figs. 2, 3). The pentosidine level ranged from abouf equal fo a manifold of the level in sound dentin. The formation of pentosidine can only account for a fraction of the increase in 328/378 fluorescence, which is in accordance with a major contribution from a different fluorophore as stated above. Unfortunately, an increase of dify-rosine as expected from fhe gain in 317/407 fluorescence (fable 2) could not be substantiated unequivocally by HPLC analysis because dityrosine co-eluted with lysylpyridinoline. Even if we would consider dityrosine to originate the lysylpyridinoline peaks observed in HPLC of carious dentin, but not of sound dentin, only one quarter of the increase in 317/407 fluorescence would derive from difyrosine. 

Interestingly, sound human dentin contained a more or less constant level of the advanced Maillard products, pentosidine and car-boxymethyllysine, irrespective of age (fable 3). Alfhough human denfin collagen is not turned over and the advanced products should thus increase during life, we suggesf fhaf fhe Maillard reacfion occurs in pre-denfin collagen, but is halted upon mineralization. ... 

Dyer DG, Blackledge JA, Thorpe SR and Baynes JW (1991b) Formation of pento-sidine during nonenzymatic browning of proteins by glucose identification of glucose and other carbohydrates as possible precursors of pentosidine in vivo. J Biol Ghem 266,11654-11660. 

Bank RA, Beekman B, Verzijl N, De Roos JADM, Sakkee AN and Te Koppele JM (1997) Sensitive fluorimetric quantitation of pyridinium and pentosidine crosslinks in biologic samples using a single HPLC-run. J Chromatogr (in press). 

Bar, K. J., Franke, S., Wenda, B., Muller, S., Kientsch-Engel, R., Stein, G., and Sauer, H. (2002). Pentosidine and N(epsilon)-(carboxymethyl)-lysine in Alzheimer s disease and vascular dementia. Neurobiol. Aging 24, 333-338. 

Shiraki, M., Kuroda, Y., Tanaka, S., Salto, M., Fukunaga, M., and Nakamura, T. (2008). Nonenzymic collagen cross-links induced by glycoxidation (pentosidine) predicts vertebral fractures. J. Bone Miner. Metab. 26, 93-100. 

When /Tcasein was heated with glucose or ribose, the fluorescence emission spectra did not differ significantly, but, with increased pressure, the spectra from the former system became less pronounced, whereas those from the latter increased in intensity and developed a shoulder at 385 nm, corresponding to that of pentosidine (see Chapter 8). An equimolar mixture of Aa-acetyllysine, /V -acctylargininc, and ribose was therefore subjected to increasing pressure.112 The pentosidine content increased about sixfold at 600 MPa when compared with that at atmospheric pressure. The pentosidine content of /1-casein similarly treated with ribose at atmospheric pressure and at 600 MPa increased from not detectable (<32 jig per 100 g protein) to 4.8 mg per 100 g protein, respectively. 

Sekine et al391 have determined urinary pentosidine and pyrraline in 75 diabetic (retinopathy none 21, simple 26, proliferative 28), 50 nephropathic (diabetic 24), and 22 control volunteers. Urinary pentosidine was increased in diabetic patients, the proliferative retinopathy group giving the highest levels. However, urinary pyrraline did not increase. There was good correlation between the pentosidine levels in urine... 

---