Traditional epidemiological studies have identified a number of risk factors for various diseases using regression-based methods that examine the association between an exposure and an outcome (i.e., one-to-one correspondences). One of the major limitations of this approach is the “black-box” aspect of the analysis, in the sense that this approach cannot fully explain complex relationships such as biological pathways. With high-throughput data in current epidemiology, comprehensive analyses are needed. The network approach can help to integrate multi-omics data, visualize their interactions or relationships, and make inferences in the context of biological mechanisms. This review aims to introduce network analysis for systems epidemiology, its procedures, and how to interpret its findings.

Traditional epidemiological studies have identified a number of risk factors for various diseases using regression-based methods that examine the association between an exposure and an outcome (i.e., one-to-one correspondences). One of the major limitations of this approach is the “black-box” aspect of the analysis, in the sense that this approach cannot fully explain complex relationships such as biological pathways. With high-throughput data in current epidemiology, comprehensive analyses are needed. The network approach can help to integrate multi-omics data, visualize their interactions or relationships, and make inferences in the context of biological mechanisms. This review aims to introduce network analysis for systems epidemiology, its procedures, and how to interpret its findings.

OBJECTIVES: Lifestyles, including exercise behaviors, change continually over time. This study examined whether the clinical biomarkers (CBs) related to cardiometabolic diseases (CMDs) and their relationships differed with changes in exercise behavior. METHODS: The Ansan-Ansung cohort study (third to fifth phases; n=2,668) was used in the current study. Regular exercise behavior was investigated using a yeso questionnaire. Changes in exercise behavior were classified into 4 groups: Y-N, N-Y, Y-Y, and N-N, with “Y” indicating that a participant regularly engaged in exercise at a given time point and “N” indicating that he or she did not. Fourteen CBs related to CMDs were used, and the associations between changes in exercise behavior and relative changes in CBs were examined. CB networks were constructed and topological comparisons were conducted. RESULTS: Y-N was associated with increases in fasting blood sugar and insulin levels in men, and increased total cholesterol and low-density lipoprotein cholesterol levels in women. Meanwhile, N-Y was inversely associated with body fat percentage, visceral fat percentage, fasting insulin, and triglyceride level. Waist circumference played a central role in most networks. In men, more edges were found in the N-Y and Y-Y groups than in the N-N and Y-N groups, whereas women in the N-Y and Y-Y groups had more edges than those in the N-N and Y-N groups. CONCLUSIONS Consistent exercise or starting to engage in regular exercise had favorable effects on CBs related to CMDs, although their network patterns differed between the sexes.

Background: As the genetic variants of trabecular bone microarchitecture are not well-understood, we performed a genome-wide association study to identify genetic determinants of bone microarchitecture analyzed by trabecular bone score (TBS). Methods: TBS-associated genes were discovered in the Ansung cohort (discovery cohort), a community-based rural cohort in Korea, and then validated in the Gene-Environment Interaction and Phenotype (GENIE) cohort (validation cohort), consisting of subjects who underwent health check-up programs. In the discovery cohort, 2,451 participants were investigated for 1.42 million genotyped and imputed markers. Results: In the validation cohort, identified as significant variants were evaluated in 2,733 participants. An intronic variant in iroquois homeobox 3 (IRX3), rs1815994, was significantly associated with TBS in men (P=3.74E-05 in the discovery cohort, P=0.027 in the validation cohort). Another intronic variant in mitogen-activated protein kinase kinase 5 (MAP2K5), rs11630730, was significantly associated with TBS in women (P=3.05E-09 in the discovery cohort, P=0.041 in the validation cohort). Men with the rs1815994 variant and women with the rs11630730 variant had lower TBS and lumbar spine bone mineral density. The detrimental effects of the rs1815994 variant in men and rs11630730 variant in women were also identified in association analysis (β=–0.0281, β=–0.0465, respectively). Conclusion In this study, the rs1815994 near IRX3 in men and rs11630730 near MAP2K5 in women were associated with deterioration of the bone microarchitecture. It is the first study to determine the association of genetic variants with TBS. Further studies are needed to confirm our findings and identify additional variants contributing to the trabecular bone microarchitecture.

PURPOSE: The high mobility group box 1 (HMGB1) protein has roles in apoptosis and immune responses by acting as a ligand for receptor for advanced glycation end products (RAGE), Toll-like receptors (TLRs), and triggering receptor expressed on myeloid cells 1. In particular, HMGB1/RAGE is involved in tumor metastasis by inducing matrix metalloproteinase 2 (MMP2) and MMP9 expression. We investigated the associations between genetic variations in HMGB1-related genes and disease-free survival (DFS) and overall survival (OS) in Korean female breast cancer patients. METHODS: A total of 2,027 patients in the Seoul Breast Cancer Study were included in the analysis. One hundred sixteen single nucleotide polymorphisms (SNPs) were extracted from eight genes. A multivariate Cox proportional hazards model was used to estimate the hazard ratio and 95% confidence interval (CI) of each SNP. The effects of the SNPs on breast cancer prognosis were assessed at cumulative levels with polygenic risk scores. RESULTS: The SNPs significantly associated with DFS were rs243867 (hazard ratio, 1.26; 95% CI, 1.05–1.50) and rs243842 (hazard ratio, 1.24; 95% CI, 1.03–1.50); both SNPs were in MMP2. The SNPs significantly associated with OS were rs243842 in MMP2 (hazard ratio, 1.33; 95% CI 1.03–1.71), rs4145277 in HMGB1 (hazard ratio, 1.29; 95% CI, 1.00–1.66), rs7656411 in TLR2 (hazard ratio, 0.76; 95% CI, 0.60–0.98), and rs7045953 in TLR4 (hazard ratio, 0.50; 95% CI, 0.29–0.84). The polygenic risk score results for the DFS and OS patients showed third tertile hazard ratios of 1.72 (95% CI, 1.27–2.34) and 2.75 (95% CI, 1.79–4.23), respectively, over their first tertile references. CONCLUSION: The results of the present study indicate that genetic polymorphisms in HMGB1-related genes are related to breast cancer prognosis in Korean women.
Advanced Glycosylation End Product-Specific Receptor ; Apoptosis ; Breast Neoplasms* ; Breast* ; Disease-Free Survival ; Female ; Genetic Predisposition to Disease* ; Genetic Variation ; HMGB1 Protein ; Humans ; Matrix Metalloproteinase 2 ; Myeloid Cells ; Neoplasm Metastasis ; Polymorphism, Genetic ; Polymorphism, Single Nucleotide ; Prognosis* ; Proportional Hazards Models ; Seoul ; Toll-Like Receptors