Proteomics in Forensic Sciences: Identification of the Nature of the Last Meal at Autopsy

A long-term psychiatric 40 years-old
male patient was found dead
at 9:00 a.m. in the clinic where he lived. Death was caused by traumatic
injuries, which the sanitary staff imputed to a fall. Nurses declared
that the patient refused having breakfast, whereas at autopsy the
stomach contained 350 g of whitish semifluid material. Using both
shotgun and gel-based proteomics, we demonstrated that the chyme contained
partly digested milk- and bread-derived proteins, eaten during a recent
breakfast. The conflict between evidence and assertions of the attending
sanitary staff prompted the Legal Authority to undertake detailed
investigations to ascertain facts and possible responsibilities. The
herein characterization provides insights in the in vivo mechanisms
of gastric breakdown of food proteins in a real meal. β-lactoglobulin
was partially resistant to gastric digestion as confirmed by Western
blot analysis, in contrast to caseins and wheat gluten proteins, which
had been degraded by gastric fluids. In addition to a complex pattern
of gastric proteins (e.g., mucin-5AC, pepsin A-3, pepsinogen C, gastric
lipase, gastrokine-2, trefoil factors), chyme contained intact proteins
and variably sized food-derived polypeptides arising from peptic and
nonpeptic proteolytic cleavage as well as heterodimeric disulfide-cross-linked
peptides. These findings suggest that the current analytical workflows
offer only a partial picture of the real complexity of the human “digestome”.