Abstract
Forensic diagnosis of fatal hypothermia is considered difficult because there are no specific findings. Accordingly, exploration of novel fatal hypothermia-specific findings is important. To elucidate the molecular mechanism of homeostasis in hypothermia and identify novel molecular markers to inform the diagnosis of fatal hypothermia, we focused on microRNA expression in skeletal muscle, which plays a role in cold-induced thermogenesis in mammals. We generated rat models of mild, moderate, and severe hypothermia, and performed body temperature-dependent microRNA expression analysis of the iliopsoas muscle using microarray and quantitative real-time PCR (qRT-PCR). The results show that rno-miR-374-5p expression was significantly induced only by severe hypothermia. Luciferase reporter assay and qRT-PCR results indicated that Mex3B expression was regulated by rno-miR-374-5p and decreased with decreasing body temperature. Gene ontology analysis indicated the involvement of Mex3B in positive regulation of GTPase activity. siRNA analysis showed that Mex3B directly or indirectly regulated Kras expression in vitro, and significantly changed the expression of apoptosis-related genes and proteins. Collectively, these results indicate that rno-miR-374-5p was activated by a decrease in body temperature, whereby it contributed to cell survival by suppressing Mex3B and activating or inactivating Kras. Thus, rno-miR-374-5p is a potential supporting marker for the diagnosis of fatal hypothermia.
Highlights
Diagnosis of fatal hypothermia is carried out based on a combination of several common findings, such as the difference in colour between blood from the right and left ventricles, Wischnewski’s spot, haemorrhage of iliopsoas muscle and so on, which are often observed in corpses exposed to c old[1,2,3,4]
As corpses are often found after a postmortem interval, examinations often do not represent the state at the time of death
We focused on four miRNAs because the 100 target mRNAs were shown to be primarily controlled by these four miRNAs
Summary
Diagnosis of fatal hypothermia is carried out based on a combination of several common findings, such as the difference in colour between blood from the right and left ventricles, Wischnewski’s spot, haemorrhage of iliopsoas muscle and so on, which are often observed in corpses exposed to c old[1,2,3,4]. These findings are observed in other pathologies such as carbon monoxide poisoning, hydrocyanic acid poisoning, and stress[5,6,7]. The aim of this study was to elucidate the molecular mechanism in iliopsoas muscle during the course of fatal hypothermia, and identify useful molecular markers for the diagnosis of fatal hypothermia
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