Transplanted Feces from Thin People Improve Insulin Sensitivity in People with Pre-Diabetes

European researchers have reported that when they transplanted fecal matter from healthy thin people into obese people with pre-diabetes, the latter group’s insulin sensitivity notably increased. (Insulin sensitivity is the body’s ability to properly use the insulin hormone to regulate the amount of glucose in the bloodstream. Pre-diabetes exists when increasing resistance to insulin creates higher-than-normal blood sugar levels, a precondition to the onset of full-blown type 2 diabetes.)

The team of scientists, led by Anne Vrieze, MD, of the Academic Medical Center in Amsterdam, Netherlands, focused on 18 obese men, aged 21 to 65 years, who had been diagnosed with metabolic syndrome. (The term, which describes a cluster of conditions, is often used interchangeably with pre-diabetes.) The men were not taking medications for their condition and had not received antibiotics within the previous 90 days.

After the men’s bowels were thoroughly cleansed, feces were transplanted into them that came either from thin male donors or, as a control, from stools that they themselves had produced.  Both sources of fecal matter had been tested for parasites and infectious agents.

Over the six-week experiment, neither group experienced weight loss, an effect that had been seen in experiments with animals. But peripheral insulin sensitivity improved greatly in the men who had received transplanted matter from outside donors versus those who had been implanted with their own fecal matter. Vrieze attributed that increase to effects of the transplantation because there had been no changes in the men’s diet or physical activity.

Although the results of the study are promising, the use of gut bacteria to affect pre-diabetes is still at a very early research phase. Fecal transplantation is not a new line of research, but Vrieze’s study is the first to focus on fecal transplantation’s possible effects on metabolic syndrome. Previous studies had focused on the use of fecal matter to restore and rebalance gut bacteria in laboratory animals and humans.

Several U.S. medical centers have looked at fecal transplantation as a possible therapy for people with stubborn gastrointestinal infections caused by the bacterium Clostridium difficile. In such cases, “good” gastrointestinal bacteria are wiped out by antibiotics in medical treatments, leaving the digestive tract open to overpopulation by the robust, antibiotic-resistant Clostridium difficile. Implanting fecal matter in affected patients introduces new bacteria that quickly reproduce, reducing the amount of  Clostridium difficile. Their presence dampens the diarrhea and abdominal bloating commonly associated with Clostridium difficile infection. 

Given the small size and limited duration of Vrieze’s study, the connection between transplanted fecal matter and an increase in insulin sensitivity is suggestive, but not conclusive. Her results open the door to much bigger and longer studies that will try to establish that differences in individuals’ gut biota, products of genetics and family environments, could become a tool against diabetes. As researchers increasingly scrutinize digestive system bacteria as a key factor in the development and progression of diabetes, a therapy aimed at changing the gut’s biota does not seem as farfetched as it would have only a few years ago.

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