Working with fruit flies, researchers have found that adult intestinal stem cells “respond to increased food intake by producing more intestinal cells, expanding the size of the intestines as long as the food keeps flowing”.
This situation is reversed upon withdrawal of food.
Prior to this research, it was believed that once embryonic stem cells mature into adult stem cells, they sit quietly in our tissues, replacing cells that die or are injured but doing little else.
“When flies start to eat, the intestinal stem cells go into overdrive, and the gut expands,” said UC Berkeley post-doctoral fellow Lucy O’Brien. “Four days later, the gut is four times bigger than before, but when food is taken away, the gut slims down.”
Just as in humans and other mammals, O’Brien added, the fly intestine secretes its own insulin. In flies, intestinal insulin seems to be the signal that makes stem cells “supersize the gut.”
“Because of the many similarities between the fruit fly and the human, the discovery may hold a key to understanding how human organs adapt to environmental change,” said David Bilder, UC-Berkeley associate professor of molecular and cell biology.
Details of the Study
O’Brien, Bilder and their colleagues discovered that when fruit flies feed, their intestines secrete insulin locally, which stimulates intestinal stem cells to divide and produce more intestinal cells.
“The real surprise was that the fruit fly intestine is capable of secreting its own insulin,” BIlder said. “This intestinal insulin spikes immediately after feeding and talks directly to stem cells, so the intestine controls its own adaptation.”
Stem cells can divide either asymmetrically, producing one stem cell and one intestinal cell, or symmetrically, producing two stem cells. The team found that, in response to food, intestinal stem cells underwent symmetric division more frequently than asymmetric division, which had the effect of maintaining the proportion of stem cells to intestinal cells, and is a more efficient way of ramping up the total number of cells, O’Brien said.
“Adaptive resizing of the intestine makes sense from the standpoint of physiological fitness,” she said. “Upkeep of the intestinal lining is metabolically expensive, consuming up to 30 percent of the body’s energy resources. By minimizing intestinal size when food is scarce, and maximizing digestive capacity when food is abundant, adaptive intestinal resizing by stem cells helps animals survive in constantly changing environments.”
I have no idea where researchers are actually going to go with this research, but I bet there is a lab geek out there right now dreaming of making a bazillion dollars by designing a stem cell therapy to control this effect.
Because if they can reduce the size of your intestines, they also reduce the travel time of food from ingestion to elimination and reduce the amount of calories absorbed and potentially stored as body-fat.
And considering the drastic increase in obesity worldwide, there is definitely a market for a solution such as this.