RESUMEN
d-amino acids have been actively examined since improved analytical techniques revealed their presence in animal bodies. Although D-Asp was identified in mammals earlier than D-Ser, research on D-Asp has lagged behind that on D-Ser, mainly because the target protein of D-Asp remains unknown. To date, the only reported functions of D-Asp are its roles in reproduction and suggested neuromodulatory functions. Since d-amino acids are also present in food, it is important to clarify their effects on gastrointestinal epithelial cells, which are always contacted after ingestion. Therefore, the present study examined the effects of d-amino acids on gastrointestinal tract basal cells. The effects of 11 types of amino acids (Ala, Arg, Asn, Asp, Gln, Glu, Leu, Lys, Pro, Ser, and Val) on the proliferation of three types of gastrointestinal epithelial cells (HGC-27, IEC-6, and Caco-2) were assessed. Although the proliferation of HGC-27 and Caco-2 was not affected by any of the 11 types of L- and d-amino acids, D-Asp inhibited the proliferation of IEC-6, derived from small intestinal epithelial cells, in concentration- and exposure time-dependent manners. The present study also examined uptake transporters, metabolic enzymes, and insulin signaling pathways; however, the mechanisms underlying the inhibitory effects of D-Asp on the proliferation of IEC-6 were not elucidated. A more detailed understanding of these mechanisms may lead to the development of pharmaceuticals as main drugs or formulation materials. Further studies are warranted on the physiological effects of d-amino acids, including D-Asp.
RESUMEN
A man in his 50 s, who was found vomiting and in a disturbed state when the emergency medical team arrived, then went into cardiopulmonary arrest during transport and died without responding to resuscitation. The hospital initially suspected that the death may have been caused by internal causes, but since the deceased had previously been transported to the hospital in a suicide attempt, the hospital called police regarding suspicions of unnatural death. The police investigation revealed two empty bottles of nicotine liquid for e-cigarettes in his house and a search history of "nicotine suicide" on his cellphone. In a forensic autopsy, he was found to be highly obese, and abundant fat deposits were observed in his organs. A stent was placed in the aorta, but no abnormality was found. There was no obvious stenosis or obstruction in the coronary arteries. Drug screening using liquid chromatography tandem mass spectrometry (LC-MS/MS) was performed on cardiac blood, urine, and stomach contents collected at autopsy, which revealed the presence of some medical products such as aripiprazole, nicotine, and cotinine. Further quantitative testing revealed high concentrations of nicotine in all samples. The left and right femoral venous blood concentrations were above the lethal dose, suggesting that arrhythmia or respiratory failure due to nicotine intoxication was the cause of death. With the widespread use of e-cigarettes, high concentrations of nicotine are readily available, and case reports of serious nicotine addiction are increasing. It is important to always consider addiction when conducting forensic evaluations in the medical field.