We have long observed that obese individuals appear to be a higher risk for developing age-related diseases such as type-2 diabetes, heart disease, osteoarthritis, and certain types of cancer. However, until now, scientists have been unable to make a correlation between obesity and age-related diseases because there has been no clear method on how to measure and compare tissue aging.
Scientists have now come up with a way to measure the biological age of your tissues using the epigenetic clock. The epigenetic clock measures DNA methylation, which are chemical markers that change in response to environmental stimuli such as stress, poor diet, and exercise. Horvath and his colleagues applied the epigenetic clock to 1,215 human samples and showed that obese individuals–people with high body mass indices (BMIs)–experienced accelerated epigenetic aging in their liver tissues. That is, the liver tissue of a person with a high BMI exhibited an older biological age than the person’s actual chronological age. For every 10 BMI units a person gains, he or she experiences an approximate 3.3-year increase in age. Studies also suggested that the accelerated aging effects due to obesity is irreversible in the short term: following bariatric surgery and rapid weight loss, study participants did not experience a reversal in their liver tissue age.
Now that the scientists demonstrated a link between obesity and accelerated aging effects, they looked to explore the question–are there particular genes that could be responsible for or result from age-related liver diseases? Scientists studied the gene expression levels in the liver and were able to identify sets of genes that were overexpressed in normal-aged livers and overexpressed in older livers. This further suggests to us that a link exists between certain biological processes and the progression of age-related liver diseases–however, we need to do more studies to understand the mechanistic cause-and-effect relationship between obesity and liver aging.
This study highlights the relationship between obesity and aging of the liver tissue and gives us insight into how obesity lends itself as a risk factor towards developing liver-related diseases such as insulin resistance and liver cancer. It’s important to note in this study that the scientists used BMI as an indicator of obesity, when in fact BMI cannot distinguish between fat and muscle mass. The scientists proposed future studies to look at the link between the accelerated aging and muscle tissue age. Regardless, understanding that obesity can affect the development of age-related diseases underscores the importance for us to maintain healthy lifestyles.