Beyond the Bench
CASE STUDY 7: At the Kitchen Table
Mindy Mamelak has been assembling a lot of meals lately — boxes filled with fig bars, string cheese, pasta with meat sauce, and peanut butter and honey sandwiches. It might sound like she’s packing lunches for Meals on Wheels, but Mamelak, a bionutritionist, is actually handling a key element of an investigation into the link between obesity and a gut-dwelling microbe. The food is for 11 people enrolled in a pilot study that takes the research from the Cedars-Sinai lab to their kitchen table, and back.
The study is the brainchild of Ruchi Mathur, MD, director of the Anna and Max Webb & Family Diabetes Outpatient Treatment and Education Center at Cedars-Sinai, and is funded by the American Diabetes Association. Dr. Mathur has pinpointed a microbe that, when overpopulated, makes people more prone to obesity and pre-diabetic conditions. For every one of our own cells, we host 10 others such as bacteria, fungi, and a plethora of other microscopic agents. These tiny entities form what’s called the microbiome, a relatively new frontier for researchers who have only begun to examine how this internal ecosystem might affect the function of our bodies. Her lab is testing how efficiently people digest food with and without that microbe — which has a mouthful of a name: Methanobrevibacter smithii or M. smithii for short.
“People ask me, ‘Why would gut microbes want you to gain weight?’” says Dr. Mathur. “From an evolutionary perspective, when we were cavemen, we sometimes had to club breakfast and then go three or four days without eating. Humans who could store calories better were more likely to survive.” Fast-forward several millennia and most Americans don’t go three or four hours without eating. “What was adaptive for our ancestors — having microbes that are really good at harvesting nutrition — might be maladaptive for our modern age and environment,” explains Dr. Mathur.
Participants who appear to have an overabundance of M. smithii take home a three-day supply of Mamelak’s custom-made meals. “We carefully design meals that match each subject’s metabolism,” says Mamelak. Subjects then take a 10-day course of antibiotics to cull the population of M. smithii. Then the three-day diet is repeated. “We are measuring people’s digestion and metabolism before and after the antibiotic, so it’s vital that they be on a standardized diet,” says Dr. Mathur.
Metabolic measurements include the use of a “smart pill” to track the speed of digestion — an electronic capsule swallowed by subjects that transmits data to a wearable device. “If the gut is emptying more slowly due to the presence of these microbes, that might encourage weight gain,” she explains. This study is shedding light, one meal at a time, on how the mass of microorganisms thriving in our gut affects our health. The findings may ultimately help inspire patient-specific antibiotics and probiotics that help people maintain a healthy metabolism.