Intestinal bacteria can predict which women will gain weight after chemotherapy...

Researchers from Bar-Ilan University and the Galilee Medical Center Researchers Prof. Omri Koren and Dr. Ayelet Shai believe that prevention can be tested using appropriate probiotics

Chemotherapy can save lives, but it comes at the cost of many side effects. One of the well-known and common symptoms among breast cancer patients is weight gain. New research points to a link between the gut bacterial population and the phenomenon.

In recent years, many studies have shed light on the connection between the microbiome – the population of intestinal bacteria that exists in the body of each and every one of us – and different health and disease conditions. The composition of the microbiome and the balance between the bacterial strains includes extensive effects on our mental and physical function. New research suggests a link between gut bacteria and weight gain among chemotherapy-treated breast cancer patients. The research was initiated by Dr. Ayelet Shai, director of the oncology department at the Galilee Medical Center, and led it together with Prof. Omri Koren of the Azrieli Faculty of Medicine at Bar-Ilan University. The research findings were published in the prestigious journal BMC Medicine.

Dr. Shay said that symptoms she had witnessed as an oncologist led her to initiate the study: “In clinical work with women recovering from breast and gynecological tumors, I have seen many women gain weight following the treatments, and have difficulty returning to their previous weight. The phenomenon is also known from the medical literature. When I read about the link between microbiome and obesity in people without cancer, I thought it would be very interesting to see if the microbiome of patients is one of the causes of obesity and other metabolic changes. “

According to the professional literature, about 30% of breast cancer patients who receive chemotherapy gain weight, but it is not known why some women gain weight and others do not. Beyond weight gain, chemotherapy is also known to increase the risk of high blood pressure and glucose intolerance, which is a pre-diabetic condition. Although this is a known phenomenon, the mechanisms underlying these processes have not been defined so far.

The study by Dr. Shai and Prof. Koren involved 33 women who were about to start chemotherapy for breast cancer and gynecological cancer. The women were weighed once before the treatment, and again about five weeks after it began. Prior to treatment, a fecal sample was also used, which was used to genetically characterize the microbiome in each of the women.After several weeks of chemotherapy, the microbiome composition was re-examined and found to have significantly changed in women who gained weight.The change was reflected in a smaller variety of Intestinal bacteria and strains of bacteria that were different from those found in women who did not experience weight gain.One important study finding is that in women who gained weight, the microbiome was characterized by low variability between the bacteria even before starting treatment.

The study showed that the composition of intestinal bacteria may predict which of the women undergoing chemotherapy will gain weight. In addition, when the gut bacteria of the weight women were transplanted into the intestines of sterile mice (i.e. without their own microbiome), the mice developed intolerance to sugar and in their blood were found signs of chronic inflammatory condition. These findings suggest that bacteria are part of the causes of metabolic changes that lead to weight gain following chemotherapy treatment.

Dr. Shay and Prof. Koren are currently in the midst of a follow-up study, which aims to examine the effects found in a larger patient population and to examine the microbiome of women at the end of treatment to understand the effect of treatment on bacterial composition. In addition, the researchers plan to test the effect of chemotherapy On obesity in sterile mice that have undergone fecal transplantation of women, and to see if there is a difference between mice implanted in their digestive tract feces from women who have gained weight compared to mice that have received feces from women who have not gained weight.

If the results obtained in the initial study are repeated, Dr. Shai notes, it will be possible to consider a stool test for women before starting treatment, so that the patient knows if she is at risk of gaining weight. In addition, prevention can be tested by a proper diet and even a probiotic.

“We hope that in the future we will be able to locate by simple examination the women who are at risk for weight gain and perhaps even suggest ways to prevent this phenomenon,” said Dr. Shai and Prof. Koren.