We designed an experiment to analyze the gut content of Rotifera based on DNA barcoding and tested it on Asplanchna sp. in order to ensure that the DNA extracted from the rotifer species is from the food sources within the gut. We selected ethanol fixation (60%) to minimize the inflow effects of treated chemicals, and commercial bleach (the final concentration of 2.5%, for 210 s) to eliminate the extracellular DNA without damage to the lorica. Rotifers have different lorica structures and thicknesses. Therefore, we chose a pretreatment method based on Asplanchna sp., which is known to have weak durability. When we used the determined method on a reservoir water sample, we confirmed that the DNA fragments of Chlorophyceae, Diatomea, Cyanobacteria, and Ciliophora were removed. Given this result, Diatomea and cyanobacteria, detected from Asplanchna, can be considered as gut contents. However, bacteria were not removed by bleach, thus there was still insufficient information. Since the results of applying commercial bleach to rotifer species confirmed that pretreatment worked effectively for some species of rotifers food sources, in further studies, it is believed to be applicable to the gut contents analysis of more diverse rotifers species and better DNA analysis techniques by supplementing more rigorous limitations.

Chum salmon (Oncorhyncus keta) is a cold-water species reported to migrate within a wide range of habitats, including Korea, Japan, North America, and Russia, playing important roles in the river–sea nutrient cycle and food web. However, research on this species has not been widely performed in South Korea owing to its geographical location at the southern edge of migration. In this study, we analyzed the spatial distribution and morphological characteristics of chum salmon migrating to South Korea using the length–weight relationship. We also analyzed 3 years of catch, sex ratio, and individual information (total length (cm), weight (kg), n = 4400) from ten rivers (eight in the East coast and two on the South coast) with a total of 17 years of water quality and the distance they traveled (n = 50) using multivariate analysis. As a result, we discovered a trend of less migration in the southern part of South Korea for all individuals migrating to South Korea. Furthermore, the weight ratio of males/females was significantly different (p < 0.05). Based on the length–weight relationship analysis, the a and b values were between 0.0011 and 0.038 and 2.65 and 3.49, respectively. In the correlation analysis, catch is negatively correlated with distance traveled and temperature (p < 0.05), and positively correlated with pH, dissolved oxygen, distance, and female ratio (p < 0.05). This is possibly the result of differences in water quality during early life stages or the presence of an estuarine barrage at the mouth of the Nakdong River. This research may be used as fundamental distribution and morphological variations of chum salmon in South Korea.

Oxidative stress is a hallmark of carcinogenesis, yet the epigenetic mechanisms linking the lifestyle-based Oxidative Balance Score (OBS) to cancer risk remain poorly understood. This study investigated the epigenetic bridge between OBS and pan-cancer susceptibility using a multi-cohort approach integrating population-based and cancer genomic data. We calculated OBS based on 16 dietary and lifestyle factors (including dietary fiber, vitamins, minerals, physical activity, smoking, alcohol, and BMI) for 2749 participants from the Korean Genome and Epidemiology Study (KoGES) and identified OBS-associated CpG sites via epigenome-wide association analysis. These markers were validated against The Cancer Genome Atlas (TCGA) pan-cancer dataset using a novel Hybrid Pi-score (HyPi) to quantify the directional consistency between OBS-driven methylation in healthy individuals and cancer-specific epigenetic alterations across three clinical comparisons: normal vs. tumor, survival outcomes, and tumor stage. We observed profound sex-specific epigenetic signatures, with zero overlap in the top 200 OBS-associated CpG sites between males and females, underscoring fundamental sexual dimorphism in oxidative stress-epigenome interactions. Notably, the top 20 OBS-associated CpGs demonstrated strong directional consistency with multiple cancer types in TCGA, particularly in kidney renal clear cell carcinoma and lung adenocarcinoma, exhibiting methylation patterns inversely correlated with tumorigenesis. Mechanistically, these findings support the role of one-carbon metabolism and vitamin C-dependent DNA demethylation pathways in mediating OBS effects. Our study provides the first evidence of an epigenetic link between lifestyle-based oxidative balance and pan-cancer risk, highlighting the utility of the HyPi score as a novel sex-specific predictive biomarker for cancer prevention. These results suggest that optimizing oxidative balance through precision nutrition may epigenetically modulate cancer susceptibility, opening new avenues for personalized prevention strategies.