Targeted quantification of N-1- valine peptides of [beta]-hemoglobin for better diagnostics in diabetes

• Published in: Clinical proteomics Vol. 13; no. 1
• Main Authors: Jagadeeshaprasad, Mashanipalya G, Batkulwar, Kedar B, Meshram, Nishita N, Tiwari, Shalbha, Korwar, Arvind M, Unnikrishnan, Ambika G, Kulkarni, Mahesh J
• Format: Journal Article
• Language: English
• Published: BioMed Central Ltd 29-03-2016
• Subjects: Care and treatment; Diabetes; Diagnosis; Genetic aspects; Peptides; Physiological aspects; Prediabetic state; India
• ISSN: 1542-6416
• DOI: 10.1186/s12014-016-9108-y

Background N-1-(Deoxyfructosyl) valine (DFV) [beta]-hemoglobin ([beta]-Hb), commonly referred as HbA1c, is widely used diagnostic marker in diabetes, believed to provide glycemic status of preceding 90-120 days. However, the turnover of hemoglobin is about 120 days, the DFV-[beta]-Hb, an early and reversible glycation product eventually may undergo irreversible advanced glycation modifications such as carboxymethylation or carboxyethylation. Hence quantification of N-1-(carboxymethyl) valine (CMV) and N-1-(carboxyethyl) valine (CEV) peptides of [beta]-Hb would be useful in assessing actual glycemic status. Results Fragment ion library for synthetically glycated peptides of hemoglobin was generated by using high resolution-accurate mass spectrometry (HR/AM). Using parallel reaction monitoring, deoxyfructosylated, carboxymethylated and carboxyethylated peptides of hemoglobin were quantified in clinical samples from healthy control, pre-diabetes, diabetes and poorly controlled diabetes. For the first time, we report N-1-[beta]-valine undergoes carboxyethylation and mass spectrometric quantification of CMV and CEV peptides of [beta]-hemoglobin. Carboxymethylation was found to be the most abundant modification of N-1-[beta]-valine. Both CMV-[beta]-Hb and CEV-[beta]-Hb peptides showed better correlation with severity of diabetes in terms of fasting glucose, postprandial glucose and microalbuminuria. Conclusions This study reports carboxymethylation as a predominant modification of N-1-[beta]-valine of Hb, and quantification of CMV-[beta]-Hb and CEV-[beta]-Hb could be useful parameter for assessing the severity of diabetes. Keywords: Diabetes, Diagnosis, Glycation, Glycemic control, HbA1c, Mass spectrometry