Obesity accelerates epigenetic aging of human liver.
Level 4 - case-series / case-control
Cross-sectional observational analysis of human tissue datasets
PubMed 25313081 · doi:10.1073/pnas.1412759111
What was done
The authors used a DNA methylation-based biomarker of aging (epigenetic clock) to assess the relationship between body mass index (BMI) and epigenetic aging across human blood, liver, muscle, and adipose tissues. Epigenetic age acceleration in liver was analyzed across two independent datasets, adjusted for the Nonalcoholic Fatty Liver Disease (NAFLD) Activity Score, compared with tissue gene expression profiles, and evaluated for short-term reversibility following bariatric surgery.
What was found
A significant correlation between BMI and epigenetic age acceleration was observed exclusively in liver tissue (dataset 1: r = 0.42, P = 6.8 × 10⁻⁴; dataset 2: r = 0.42, P = 1.2 × 10⁻⁴), with no significant correlation detected in blood, muscle, or adipose tissue. On average, liver epigenetic age increased by 3.3 years for every 10-unit increase in BMI. This acceleration remained significant after adjusting for NAFLD Activity Score and its component traits. A set of 279 genes underexpressed in older liver samples was enriched for nuclear mitochondrial genes involved in oxidative phosphorylation and electron transport (P = 1.2 × 10⁻⁹). Short-term rapid weight loss after bariatric surgery did not reverse this epigenetic age acceleration.
Why it matters
This study shows that obesity selectively accelerates biological aging in human liver tissue rather than uniformly across all tissues. This epigenetic aging provides a potential molecular mechanism linking high BMI to liver-related comorbidities, including insulin resistance and liver cancer.
Limits
The abstract does not report participant counts or sample sizes for any tissue datasets or the surgical cohort. The observational design cannot establish direct causality, and long-term effects of sustained weight loss beyond the immediate post-bariatric surgery period were not evaluated.
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- supports Obesity significantly accelerates epigenetic aging in liver tissue.