Examining Epigenetic Age in Women with Different Obesity Conditions Using DNA Methylation at the FHL2 Gene

DNA methylation (DNAm) age estimation is one of the hottest topics in forensic contexts. However, there is growing evidence that DNAm can be affected by several factors, including many clinical conditions. In this study, we analyzed the methylation levels within the FHL2 gene in Portuguese women using the droplet digital PCR (ddPCR) methodology to develop age prediction models (APMs). We hypothesized that obesity could affect the accuracy of APMs and would be associated with the advancement in epigenetic aging. We collected blood samples from 62 women (aged 21-58 years old) with overweight and obesity. DNA extracts were subjected to bisulfite conversion followed by ddPCR using dual-labeled probes targeting the methylated and unmethylated FHL2 CpG site cg06639320. The developed APM yielded a mean absolute deviation (MAD) of 4.72 years between predicted and chronological ages in the total sample. When applying the developed APM to women classified as overweight, the MAD was 3.64 years, while, for those with obesity class 1, it was 3.93 years, and, for those with obesity class 2, 6.29 years. The same pattern of accuracy was observed when we developed APMs specifically for the groups categorized by overweight and obesity, obtaining MAD values of 3.75 years (overweight), 3.69 years (obesity class 1) and 6.24 years (obesity class 2). Our study indicates that severe obesity may impact the accuracy of DNA methylation-based age estimators. We did not find evidence of an association between BMI and accelerated epigenetic aging. However, we found signals of epigenetic age acceleration in younger subjects and epigenetic age deceleration in the older participants.