Scientists have long known that diet shapes the immune system. Now, a UC San Francisco team has found that even a brief dietary change can\u00a0substantially change\u00a0how the body responds to skin irritation, at least in mice.<\/p>\n
When\u00a0scientists\u00a0fed\u00a0mice\u00a0a high-fat diet for just a few days, the mice\u00a0had a much\u00a0worse\u00a0reaction to an irritating cream.\u00a0And the skin stayed on alert\u00a0even\u00a0after the mice returned to a low-fat\u00a0diet\u00a0and the inflammation<\/a> cleared,\u00a0responding more strongly the next time it was exposed to the cream.<\/p>\n The findings suggest that\u00a0short-term\u00a0diet may\u00a0have just\u00a0as much\u00a0an effect\u00a0as body weight\u00a0when it comes to inflammation.<\/p>\n “Long-term dietary habits absolutely matter for health, but our study unearthed a much more real-time influence of diet,” said\u00a0Sagar Bapat, MD, PhD, professor of pathology at UCSF and corresponding author of\u00a0the paper, which appears in\u00a0Nature\u00a0on October 28. “Breakfast, lunch, dinner – they all can have a tremendous and rapid impact on the immune system.”<\/p>\n The discovery grew from laboratory experiments on obesity, led by\u00a0Zewen\u00a0“Owen” Jiang, PhD, co-first author of the paper,\u00a0carried out\u00a0when he was\u00a0a\u00a0graduate student\u00a0at UCSF.<\/p>\n Jiang and his colleagues first raised mice on either low-fat or high-fat food pellets.\u00a0Then, the scientists applied imiquimod, a cream that triggers skin inflammation, to one ear of each mouse and compared what happened between the low- or high-fat diet groups.\u00a0<\/p>\n Obese mice habitually fed high-fat pellets had severe reactions to imiquimod, while mice fed with low-fat pellets had mild reactions.\u00a0<\/p>\n “For many years,\u00a0we’ve\u00a0known that obesity is tied to more severe inflammation. But we wanted to know whether it was the extra weight or simply the bad diet that was driving the stronger response,” Jiang said.<\/p>\n So, the team tested whether\u00a0just\u00a0four days on high-fat food was enough to\u00a0trigger an over-active\u00a0immune response.\u00a0They switched\u00a0mice\u00a0that had been\u00a0raised on low-fat food to\u00a0high-fat\u00a0food, and\u00a0dabbed one ear\u00a0with\u00a0imiquimod\u00a0three days later. The\u00a0normal-weight mice developed severe ear inflammation\u00a0just like\u00a0the\u00a0obese mice.<\/p>\n Likewise,\u00a0obese mice\u00a0that\u00a0had been\u00a0switched to normal food for\u00a0just\u00a0four days experienced much milder inflammation.<\/p>\n Weeks later, after the normal-weight mice had returned to a low-fat diet and\u00a0their\u00a0inflammation had subsided,\u00a0they got\u00a0a second\u00a0dose\u00a0of imiquimod\u00a0in the same ear that had flared before\u00a0–\u00a0and\u00a0it\u00a0triggered an outsized response.<\/p>\n Jiang and Bapat found that high-fat food drew rapid-response immune cells into the skin, where they amplified the reaction to imiquimod. As the inflammation subsided, other immune cells, called memory T\u00a0cells\u00a0remained in the affected ear. Together, these changes left the tissue primed for the next time.<\/p>\n The team found a similar kind of heightened inflammation in response to irritation in the lungs after just a few days of eating a high-fat diet.<\/p>\n “The diet of a laboratory mouse doesn’t map\u00a0neatly onto what we eat, but it’s striking how quickly the immune system responds to what’s happening in the body right now,” said Jiang. “Diet, exercise, sleep –\u00a0they\u00a0could\u00a0all\u00a0shape immune health in ways we don’t yet appreciate.”<\/p>\n Source:<\/p>\n University of California – San Francisco<\/a><\/p>\n Journal reference:<\/p>\n