Gut Bacteria Molecule Rebuilds NAD and Repairs Intestines

A molecule your gut bacteria make, and your own cells don't, can be turned back into one of the body's most-watched coenzymes. Researchers at Rutgers Health report in Science Advances that (amide-)N-methylnicotinamide, or N-MNA, is a precursor to nicotinamide adenine dinucleotide — NAD — and that it drives gut stem cell renewal and epithelial repair. NAD levels decline with age, and that decline is thought to be a major driver of aging itself.

The trick is a near-miss in chemistry. Human cells make an almost identical molecule when they dispose of excess NAD building blocks, but the human version can't be converted back into NAD. The bacterial version can. "Humans do not appear to make this exact precursor molecule N-MNA, but some of the bacteria living in our gut do," said senior author Nan Gao, a professor at Rutgers New Jersey Medical School. "The molecules animal cells and bacteria make are almost identical, but a tiny difference allows the conversion of the bacterial compound back into NAD itself," said senior author Xiaoyang Su of Rutgers Robert Wood Johnson Medical School.

First author Jiangmeng Han, a doctoral student at Rutgers University-Newark, tracked the molecule into human colon cells, where it supplied about 22 percent of their NAD within 24 hours. It also became NAD in human neurons, liver cells and kidney cells, and in the bodies and heads of fruit flies that were given it. Because NAD itself can't enter cells directly, a precursor that cells will take up and convert is the form researchers have been hunting.

The animal results are the dramatic part, and they should be read as animal results. In mice with inflamed and damaged colons, untreated animals lost 20 percent of their body weight and died; mice injected with N-MNA lost 5 percent and recovered. In fruit flies with damaged guts, seven-day survival rose from 43 percent to 78 percent. Those are controlled experiments in model organisms, the strongest evidence this kind of study can produce before human trials — and several steps away from a treatment.

The human data is a correlation, presented as one. In stool samples from 54 patients with inflammatory bowel disease and 20 healthy volunteers, patients with low N-MNA had significantly higher levels of gut inflammation markers. "Patients with low levels of this metabolite showed a higher inflammatory activity," Gao said. The team didn't test N-MNA treatment in those patients, and didn't test whether eating probiotic strains that make N-MNA, including Lactobacilli in yogurt and supplements, raises NAD in people. A stool test that flags likely candidates is possible, Gao said, and probably years away.

What happens next is basic science, not a product launch. The team still has to find the human enzymes that process N-MNA; one lab is testing whether the molecule supports brain cell health and longevity, another is mapping the bacterial genes that produce it. Rutgers has filed a provisional patent application on uses of N-MNA. "This compound itself may be sufficient, but we cannot rule out the possibility that there are other, better compounds," said senior author Ching-On Wong of Rutgers-Newark. That's the right register for a finding this early: a real mechanism, a striking rescue in animals, and no honest claim yet about a bottle anyone can buy.