Gut Stem Cells ‘Remember’ A High-Fat Diet, Mouse Study Finds

Fatty Food Left a Lingering Mark on Gut Cells

Cancer-prone mice that went back to a high-fat diet after a month of regular food developed bigger precancerous gut lesions than mice eating fatty food for the first time, according to a new study. Something in their stem cells seemed to carry over: changes in how their DNA was packaged had not fully reset, even after the cells went back to behaving normally.

Researchers at Arizona State University, reporting in the journal Stem Cell Reports, wanted to know whether gut stem cells simply react to dietary fat while it is on the plate or hold onto something afterward. These cells keep rebuilding the intestinal lining, and earlier work showed fatty diets push them to multiply more, raising the risk of precancerous growths. The authors also cite the established link between a Western diet and colorectal cancer risk.

Inside a cell, DNA is coiled tight, and only the loosened stretches can be read. A high-fat diet changed which stretches were loosened, and many stayed that way after the mice returned to regular food. Mice carrying those leftover changes also reacted more strongly when the fatty diet came back.

A High-Fat Diet Changed How Gut Stem Cells Package Their DNA

Researchers used mice bred so their gut stem cells glowed green, which made the cells easy to collect with a cell sorter. Matched by age and sex, the mice started their diets at 8 weeks old. Some ate standard food for 24 weeks, about six months, while others ate a high-fat Western diet. A DNA-mapping test on stem cells from seven mice per diet then showed which stretches were loosened.

Diet mostly adjusted stretches that were already loose rather than opening new ones, and the genes that make a stem cell a stem cell were not directly affected. Instead, changes gathered near genes that handle fat and genes that run immune activity. Fat-handling regions loosened while inflammation-related regions tightened, a pattern that fits a fatty diet quieting some immune signals in the gut. A 24-hour fast produced part of the same pattern, though not all of it.

Mice Back on Normal Food Kept High-Fat Diet DNA Changes for Weeks

Back on regular food, cell behavior drifted toward normal. Overactive cell division had calmed by the one-week check, but tumor-like growth took longer to settle. To test that, researchers deleted a gene called Apc in gut stem cells, a gene that normally acts as a brake on tumors and whose loss is the dominant driver of intestinal cancers. Twelve days later, lesions in mice one week off the fatty diet were still larger than in mice that always ate standard food. After four weeks off, the lesions were comparable in size. Each group held six to eight mice.

DNA packaging was slower to catch up. At one week, more than six in ten of the loosened stretches were still loose, and nearly one in five stayed that way at four weeks. Stretches the diet had tightened snapped back much faster.

Then came a diet re-challenge. Some mice ate the fatty diet for 24 weeks, regular food for four, and the fatty diet again for one week. Comparison mice ate regular food for 28 weeks before their own single week of fatty food. After that week, gut tissue from nine re-challenged mice grew more lab-dish mini-guts than tissue from 12 first-timers. In cancer-prone mice, six re-challenged animals developed larger lesions, with more dividing cells, than four first-timers.

Stem cell memory has turned up elsewhere in the body. The authors point to skin stem cells that respond more forcefully to later inflammation and blood-forming stem cells primed by an earlier immune challenge.

High-Fat Diet DNA Changes Required Fat-Sensing Proteins, Not Fat-Burning

Two fat-sensing proteins, PPAR-delta and PPAR-alpha, proved necessary. When both were genetically knocked out in the mice, the fatty diet could no longer produce its usual DNA changes, with only three left. A related protein those sensors switch on to burn fat for fuel was largely unnecessary. The sensors therefore seem to reshape DNA packaging by a route separate from fat-burning, though exactly how remains unsolved.

For scale, the cancer-driving Apc deletion remodeled roughly 100 times as many DNA stretches as diet did. Even so, nearly half of the diet-linked stretches overlapped with Apc-related ones, so part of the diet’s fingerprint carried into early lesion cells.

Mouse Results Do Not Yet Show a Human Cancer Risk

All of this happened in mice, many bred to develop intestinal lesions, so none of it measures cancer risk in people. The study found lingering DNA changes and bigger lesions side by side without proving one causes the other, and it followed the changes for only four weeks, so how long the memory lasts is unknown.

Within a month of regular food, gut cells in these mice behaved normally again, yet their DNA still carried traces of the fatty diet. Whether human gut cells hold a similar memory remains untested, but the mouse data give reason to treat a stretch of unhealthy eating as something that may not vanish the day habits improve.

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Disclaimer: This article reports on research conducted in mice and is for informational purposes only. It is not medical advice and should not be used to diagnose, treat, or prevent any condition. Anyone with questions about diet or cancer risk should consult a qualified health care professional.

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