BACKGROUND: Mitochondria, which harbor their own genome (mtDNA), have attracted attention due to the potential of mtDNA copy number (mtDNA-CN) as an indicator of mitochondrial dysfunction. Although mtDNA-CN has been proposed as a simple and accessible biomarker for metabolic disorders such as metabolic dysfunction-associated steatotic liver disease, the underlying mechanisms and the causal relationship remain insufficiently elucidated. In this investigation, we combined longitudinal epidemiological data, animal studies, and in vitro assays to elucidate the potential causal relationship between reduced mtDNA-CN and the development of steatotic liver disease (SLD). METHODS: We conducted a longitudinal study using data from a health examination cohort initiated in 1981 in Yakumo, Hokkaido, Japan. Data from examinations performed in 2015 and 2022 were analyzed, focusing on 76 subjects without SLD at baseline (2015) to assess the association between baseline mtDNA-CN and subsequent risk of SLD development. In addition, 28-day-old SD rats were fed ad libitum on a 45% high-fat diet and dissected at 2 and 8 weeks of age. Blood and liver mtDNA-CN were measured and compared at each feeding period. Additionally, in vitro experiments were performed using HepG2 cells treated with mitochondrial function inhibitors to induce mtDNA-CN depletion and to examine its impact on intracellular lipid accumulation. RESULTS: Epidemiological analysis showed that the subjects with low mtDNA-CN had a significantly higher odds ratio for developing SLD compared to high (odds ratio [95% confidence interval]: 4.93 [1.08-22.50]). Analysis of the animal model showed that 8 weeks of high-fat diet led to the development of fatty liver and a significant decrease in mtDNA-CN. A further 2 weeks of high-fat diet consumption resulted in a significant decrease in hepatic mtDNA-CN, despite the absence of fatty liver development, and a similar trend was observed for blood. Complementary in vitro experiments revealed that pharmacologically induced mitochondrial dysfunction led to a significant reduction in mtDNA-CN and was associated with increases in intracellular lipid accumulation in HepG2 cells. CONCLUSIONS Our findings suggest that reduced mtDNA-CN may contribute causally to SLD development and could serve as a convenient, noninvasive biomarker for early detection and risk assessment.
Animals ; DNA, Mitochondrial/genetics* ; Humans ; Male ; DNA Copy Number Variations ; Female ; Fatty Liver/blood* ; Rats ; Middle Aged ; Longitudinal Studies ; Rats, Sprague-Dawley ; Adult ; Japan/epidemiology* ; Aged ; Biomarkers/blood* ; Hep G2 Cells ; Diet, High-Fat/adverse effects*

Fulminant myocarditis is known as a disastrous disease that requires intensive care with mechanical cardiopulmonary support. Percutaneous cardiopulmonary bypass (PCPS), which is referred to as extracorporeal membrane oxygenation, is usually used for fulminant myocarditis. However, in some cases, PCPS may be ineffective because of circulatory insufficiency and could be associated with various severe complications such as multiple organ failure or leg ischemia. In such cases, placement of a ventricular assist device (VAD) is required. A 46-year-old man with fever and severe fatigue was admitted to a local hospital and diagnosed as having fulminant myocarditis. Although an intra-aortic balloon pump and PCPS were introduced, cardiac function was not recovered, causing multiple organ failure and leg ischemia. Hence, he was transferred to our hospital for further mechanical support. Transesophageal echocardiography (TEE) revealed severe biventricular cardiac dysfunction, and radiography showed pulmonary edema. His total bilirubin level was 6.9 mg/dl and platelet level was 3,300/μl. Thus, we implanted a biventricular assist device (BiVAD). At 12 days after the implantation, TEE revealed improvement of cardiac function, and blood biochemical examination revealed recovery of multiple organ function. Thereafter, the patient was weaned from the BiVAD successfully. After the operation, the patient underwent a long rehabilitation. He was discharged 51 days after the operation, without any neurological or cardiac complication.

The Standardized Structured Medical record Information eXchange (SS-MIX) was started in 2006 as the project supported by the Ministry of Health, Labour and Welfare (MHLW) for promoting the exchange of the standardized medical information. Free soft wares developed in the project allow the storage of medical information to receive HL7 messages for prescription, laboratory test results, diagnoses and patient demographics in the hospital information system (HIS). We encourage the use of the SS-MIX standardized storage for postmarketing surveys and clinical studies. The recommendations consist of the following 7 parts. [1] In surveys and clinical studies, the information of drugs and laboratory test results in the SS-MIX standardized storage can be directly transferred to the electronic questionnaire and the investigators may obtain the information with high accuracy and granularity. [2] The SS-MIX standardized storage works as the backup system for the HIS because it can provide the minimum information essential in patient care even under the disastrous condition like earthquake or unexpected network failure. [3] The SS-MIX standardized storage may be useful to conduct a good pharmacoepidemiology study not only because it provides the information in the storage efficiently but also it can be used to identify “new users” who started the drug after some period of non-use.The “new user” design is often essential to have the unbiased results. [4] When the drug company conducts postmarketing surveys according to the current regulation, the use of the SS-MIX standardized storage will facilitate the fast and efficient collection of data to develop the timely measure to minimize the drug-related risk. With the SS-MIX standardized storage, it is also expected that many types of study design can be employed and the quality of data is improved in the survey. [5] The SS-MIX standardized storage maybe also useful to evaluate the risk minimization action plan by comparing the prescription pattern or incidence of the targeted adverse event between two periods before and after the implementation of the action plan. [6] In planning clinical trials, the SS-MIX standardized storage may be used to estimate the size of eligible patients. The storage may also allow conducting cross-sectional studies to know characteristics of diseases or drug treatment. In addition, cohorts of those who had coronary artery angiography, new users of a drug and those with a rare disease may be readily identified. Using such cohorts, investigators can initiate a case-control study nested within the cohort, pharmacogenomic studies and comparative effectiveness researches. [7] The SS-MIX standardized storage may be used as the formal data source in clinical trials in the future when some conditions are satisfied. For instance, the formal agreement should be reached between industry, government and academia on the use of standards of data structure in Clinical Data Interchange Standards Consortium (CDISC) and on the operation of computerized system validation (CSV) in the clinical trials.