# Selective Targeting of Senescent FHs74Int Cells by Human Breast Milk Free Fatty Acids

## TL;DR

Human breast milk may help remove aging cells in the developing intestine, potentially supporting long-term gut and immune health.

## Contribution

Breast milk's free fatty acids selectively eliminate senescent intestinal cells, revealing a novel mechanism for intestinal health.

## Key findings

- Breast milk reduces senescent cell recovery without harming non-senescent cells.
- The lipid fraction of breast milk, especially free fatty acids, is responsible for its senolytic activity.
- Warming breast milk increases free fatty acid levels and enhances its ability to remove senescent cells.

## Abstract

As babies grow in the womb, their intestines undergo significant changes. Sometimes, specific cells in the intestine stop dividing and enter a state called senescence—a kind of “retirement” for cells. While this can help shape the developing intestine, if these cells aren’t cleared out properly, they might cause problems later in life. To investigate whether human breast milk—already recognized for its support of gut and immune function—could aid in the removal of senescent cells from the developing intestine, lab-grown fetal intestinal cells were exposed to breast milk, infant formula, and various milk components. Cellular responses were analyzed, with particular focus on the impact on senescent cells. Breast milk, unlike formula, appeared to selectively eliminate senescent cells while sparing most non-senescent cells. This effect was attributed to the milk’s fatty fraction, especially free fatty acids (FFAs). When breast milk was warmed, its FFA levels increased, and so did its ability to remove senescent cells. These findings highlight a novel benefit of breast milk: its potential to promote intestinal health by removing aging cells, which may be crucial for long-term gut and immune system function.

Cellular senescence is a state of irreversible growth arrest characterized by a pro-inflammatory phenotype, playing dual roles in development. In the fetal intestine, the regulation of senescent cells is critical for maintaining tissue homeostasis. Human breast milk (HBM), known for its rich composition of bioactive molecules, may play a role in modulating senescence, although its effects on senescent intestinal cells remain unexplored. This study investigated whether HBM selectively eliminates senescent cells in the FHs74Int fetal intestinal epithelial cell line. Senescence was assessed via β-galactosidase activity and expression of p16 and p21. The model cell line was treated with HBM, infant formula, and milk fractions, and outcomes included cell recovery, senescence markers, apoptosis, and mitochondrial potential. Total free fatty acids (FFA) were quantified and correlated with senolytic activity. HBM reduced senescent cell recovery without affecting non-senescent cells, correlating with decreased β-galactosidase activity, reduced phospho-p38 and γH2AX expression, mitochondrial depolarization, and caspase activation. Only the lipid fraction retained senolytic activity, which was associated with elevated FFA levels. Incubation of HBM at 37 °C increased FFA content and conferred senolytic activity. These findings are consistent with the idea that HBM exerts selective senolytic effects via FFA, revealing a novel mechanism by which breast milk could contribute to intestinal homeostasis.