A Preliminary Investigation on Placenta Protein Profile Reveals Only Modest Changes in Well Controlled Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is associated with a wide range of tissue-specific changes depending on the quality of glycemic control of the mothers. Here we tested the hypothesis that GDM is associated with alterations in the human term placenta proteome. For this aim, two different approaches were employed. The placenta homogenates from 20 healthy subjects and those from 20 GDM pregnant women were pooled. The two samples thus obtained were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and the proteins detected were tentatively identified by comparison of their molecular weight with the Human Protein Reference Database, restricting the search to the species expressed in the placenta tissue. However this approach led to misleading results: in fact, an in deep analysis of the spectra and tandem mass spectrometry (MS/MS) measurements of the digestion products from the protein detected, unequivocally proved that the species observed are maternal and fetal globins. Consequently, the two pools were analyzed by 1D sodium dodecyl sulphate polyacrylamide gel electrophoresis; the different bands obtained were digested by trypsin and the digestion products were analyzed by MALDI-MS; the protein identification was carried out by comparison of the peptide mass fingerprint with databases. Only modest quantitative differences were observed between the placenta protein profiles of healthy and GDM subjects, indicating that GDM, if well controlled, induces only minor changes in the placental proteome. One example of differently expressed proteins in the placenta homogenate pool from GDM and the controls was the SRRM1 protein, a member of the serine–arginine protein kinase family; for GDM samples, the MALDI spectrum of its digestion products showed the presence of molecular species attributable to glycation and glyco-oxidation processes.