Comparative proteomic analysis of human whole saliva of children with protein–energy undernutrition

Abstract

Objective: The aim of the present study was to investigate the protein profile of children with different levels of protein–energy undernutrition (PEU) through a proteomic approach of human whole saliva. Methods: Initially, saliva samples of children with mild, moderate, and severe PEU were collected and lyophilized. Saliva samples of healthy children were used as controls. Samples were analyzed for total protein using the Bradford method. Saliva samples were analyzed by two-dimensional electrophoresis according to their isoelectric point (pI) and their molecular weights (MWs). Results: Comparisons of protein bands among the healthy and mildly, moderately, and severely undernourished children showed significant differences in the MWs (P ¼ 0.001) and pI values (P ¼ 0.03). In total 159 spots were identified in the healthy children; 156, 168, and 221 spots were observed in mildly, moderately, and severely undernourished children, respectively. Mildly undernourished children presented with the spot with the highest MWof 293 kDa (pI ¼ 7.77) and the lowest MWof 5 kDa (pI ¼ 4.83). Moderately undernourished children were the only ones who did not present with a protein band with an MWof 30 kDa. The presence of a protein band with an MW of 123 kDa (pI ¼ 516), possibly a cyclin-dependent protein kinase, was also observed only in this group. Conclusion: The protein profile in saliva varies according to the presence or absence of PEU, and these variations are specifically expressed in different grades of undernutrition. Thus, saliva may be an important diagnostic tool for the assessment of PEU.