@article {49345,
	title = {Discovery of free glycated amines and glycated urea in diabetic plasma: potential implications in diabetes},
	journal = {ACS Omega},
	volume = {9},
	year = {2024},
	month = {MAY },
	pages = {24907-24915},
	type = {Article},
	abstract = {<p>
	The role of protein glycation in the pathogenesis of diabetes has been well established. Akin to proteins, free amino acids and other small-molecule amines are also susceptible to glycation in hyperglycemic conditions and may have a role in the pathogenesis of the disease. However, information about glycation of free amino acids and other small-molecule amines is relatively obscure. In the quest to discover small-molecule glycated amines in the plasma, we have synthesized glycated amino acids, glycated creatine, and glycated urea, and by using a high-resolution accurate mass spectrometer, a mass spectral library was developed comprising the precursor and predominant fragment masses of glycated amines. Using this information, we report the discovery of the glycation of free lysine, arginine, and leucine/isoleucine from the plasma of diabetic patients. This has great physiological significance as glycation of these amino acids may create their deficiency and affect vital physiological processes such as protein synthesis, cell signaling, and insulin secretion. Also, these glycated amino acids could serve as potential markers of diabetes and its complications. While other amines, such as creatinine and urea, accumulate in the plasma and act as biomarkers of diabetic nephropathy. For the first time, we report the detection of glycated urea in diabetic plasma, which is confirmed by matching the precursor and fragment masses with the in vitro synthesized glycated urea by using C-12(6) and C-13(6)-glucose. Further, we quantified glycated urea detected in two forms, monoglycated urea (MGU) and diglycated urea (DGU), by a targeted mass spectrometric approach in the plasma of healthy, diabetic, and diabetic nephropathy subjects. Both MGU and DGU showed a positive correlation with clinical parameters, such as blood glucose and HbA1c. Given that urea gets converted to glycated urea in hyperglycemic conditions, it is crucial to quantify MGU and DGU along with the urea for the diagnosis of diabetic nephropathy and study their physiological role in diabetes.</p>
},
	issn = {2470-1343},
	doi = {10.1021/acsomega.4c01772},
	author = {Shaikh, Rashdajabeen Q. and Das, Sancharini and Chaurasiya, Arvindkumar and Ashtamy, Murali G. and Sheikh, Amreen B. and Fernandes, Moneesha and Tiwari, Shalbha and Unnikrishnan, Ambika G. and Kulkarni, Mahesh J.}
}
@article {49810,
	title = {Characterization of S-homocysteinylation of Human Insulin and Its Implications in Diabetes},
	journal = {Protein Journal},
	volume = {44},
	year = {2025},
	month = {OCT},
	pages = {598-610},
	type = {Article},
	abstract = {<p>
	Homocysteine thiolactone is a reactive thiol known for its interaction with various proteins. Nevertheless, there exists a paucity of information concerning the interaction between homocysteine thiolactone and human insulin, particularly regarding the mechanism by which homocysteine facilitates the reduction of disulfide bonds within insulin. In the present study, we have elucidated the binding sites of homocysteine to the cysteine residues (A6-B7 and A20-B19) that are implicated in the formation of intermolecular disulfide bonds in insulin through an in vitro reaction analyzed via LC-ESI MS/MS. This results in a reduction of disulfide bonds linking the A and B chains, which was corroborated by MALDI-TOF-MS and ESI-MS analysis. The secondary structure of insulin is affected by this modification, as evidenced by circular dichroism spectroscopy. In-silico studies also show that homocysteine affects the insulin structure. A glucose uptake assay conducted in Chinese hamster ovary (CHO) cells that stably express the insulin receptor revealed that HC-modified insulin is less effective in inducing glucose uptake compared to native insulin, suggesting that HC-induced structural modifications in insulin influence functional activity. This study provides insight into the HC-induced structural and functional changes in insulin and discusses the consequent implications for diabetes.</p>
},
	keywords = {Disulfide bonds, Homocysteinylation, insulin, Mass spectrometry},
	issn = {1572-3887},
	doi = {10.1007/s10930-025-10282-9},
	author = {Sheikh, Amreen B. and Jathar, Swaraj M. and Tammara, Vaishnavi and Das, Atanu and Kulkarni, Mahesh J.}
}
