N(6)-carboxymethyllysine

A LC-MS/MS method was developed for the simultaneous determination of N(6)-carboxymethyllysine (CML) and its precursor lysine, in exhaled breath condensate (EBC). N(6)-carboxymethyllysine, or N(epsilon)-carboxymethyllysine, or abbreviated to CML, is an important biomarker of advanced glycation end products (AGEs). AGEs are formed by reaction of reducing sugars (e.g. glucose) or sugar degradation products and the amino groups of proteins (e.g. lysine) or other macromolecules. The process of AGEs accumulating in different tissues is linked to diseases such as diabetic nephropathy, diabetes mellitus, atherosclerosis, Alzheimer's diseaase, and liver cirrhosis. CML is a well-established analytical indicator of AGEs. This study revealed for the first time, that the presence of CML was detected in all EBC samples of healthy subjects and patients with diseases such as chronic obstructive pulmonary disease (COPD), diabetes, or pneumonia using highly specific LC-MS-MS method. However, this method was inappropriate for the determination of lysine. Lysine is a precursor of CML in the EBC. Separation and detection of analytes were performed by hydrophilic-ion liquid chromatography coupled with tandem mass-spectrometric detection (HILIC-MS-MS). Accuracy for analytes ranged between 89.5 and 133%. Usually, immunochemical assays are used for the analysis of CML in human body fluids or tissues; only a few studies have applied instrumental analytical methods, for example GC-MS, HPLC coupled with fluorescence detection, or tandem mass spectrometry (MS/MS) (Anal Bioanal Chem. (2007)) Description of disease(s) related to N(6)-carboxymethyllysine (CML):

Disease summary

Dialysis

No significant difference of the CML and lysine concentrations between healthy control and dialysis patients. Though the CML/lysine ratio is higher in patients undergoing dialysis, this tread does not reach the 5% level of significance (Anal Bioanal Chem. (2007)).

Summary of extracted biomedical information