Mitochondrial DNA content: a new potential biomarker for Sudden Infant Death Syndrome

Background: Sudden Infant Death Syndrome (SIDS) occurs in apparently healthy infants and is unpredictable and unexplained despite thorough investigations and enormous research efforts. The hypothesis tested in this case–control study concerns mitochondrial involvement in SIDS occurrence. Methods: Mitochondrial DNA content (MtDNAcn) was measured in 24 SIDS cerebral cortex samples and 18 controls using real-time PCR. Results: The median (interquartile range) mtDNAcn in SIDS and controls was 2578 (2224–3838) and 1452 (724–2517) copies per nuclear DNA, respectively (P = 0.0001). MtDNAcn values were higher in SIDS victims born to non-smoking parents (n = 7) 4984 (2832–6908) compared to the controls (n = 5) 2020 (478–2386) (P = 0.006). Increased levels of mtDNAcn have been observed in the SIDS cases with mild defects in nuclei not essential for life compared to those found in SIDS cases with severe alterations of respiratory function (P = 0.034) 3571 (2568–5053) (n = 14) 2356 (1909–3132) (n = 8), respectively. Conclusions: Our study revealed for the first time higher mtDNAcn in the cerebral cortex of the SIDS cases than the controls, indicating metabolic alterations. MtDNAcn plays an important role in compensatory mechanisms against environmental factors affecting human health. Despite the small sample size, mtDNA may prove to be a potential forensic biomarker for autopsied SIDS victims for gaining new insights into the etiology of SIDS. Impact: Mitochondrial DNA content evaluated in cerebral cortex samples is higher in SIDS victims than controls.These results represent a novel line of investigation for the etiology of SIDS and could have a significant role in the compensatory mechanism due to environmental factors affecting human health.These findings suggest that the mitochondria are involved in SIDS: mtDNA content may represent a biomarker of this syndrome.