Nicotinamide mononucleotide (NMN), a dietary supplement ingredient shown to increase cellular NAD levels, is thought to counteract certain aspects of aging based on its role in cellular metabolism, however, evidence on its potential benefits in humans is largely preliminary. NMN has been shown to counteract aspects of aging and improve metabolic health in mice, and the remarkable beneficial effects seen in rodents have led several global companies to market the compound as a nutraceutical.
 
NMN is a precursor to another compound in all cells, called NAD, a compound which is shown to decline with age in a broad range of animals including humans. Presence of the compound in the body, or lack thereof, has been associated with insulin resistance and other health markers in mice, and NMN supplementation slows and ameliorates age-related decline in function of the many tissues of the body in mice. However, few if any of the benefits seen in rodents have translated to benefits on human metabolism or aging, in the highly limited research that exists.
 
In a recent small clinical trial on 25 prediabetic, postmenopausal women, researchers from Washington University School of Medicine observed significant improvements to insulin sensitivity which they said warranted further investigation into any potential role that NMN could have in the metabolic health of people with obesity, prediabetes, or Type 2 diabetes. Researchers recruited only women to participate in the study due to the fact that NMN had the most pronounced effects in female mice.
 
NMN treatment improved the ability of insulin to increase glucose uptake in skeletal muscle significantly, and improved the expression of genes that are involved in muscle structure and remodeling. However, the researchers warned that NMN treatment did not lower blood glucose or blood pressure, improve blood lipid profiles, increase insulin sensitivity in the liver, reduce fat in the liver, or decrease circulating markers of inflammation, as were observed in many prior studies on rodents.
 
Nonetheless, insulin enhances glucose uptake and storage in muscle, so people who are resistant to insulin are at an increased risk of developing Type 2 diabetes.
 
“Although our study shows a beneficial effect of NMN in skeletal muscle, it is premature to make any clinical recommendations based on the results from our study,” senior investigator Samuel Klein, MD, the William H. Danforth Professor of Medicine and Nutritional Science and director of the Center for Human Nutrition, said. “Normally, when a treatment improves insulin sensitivity in skeletal muscle, as is observed with weight loss or some diabetes medications, there also are related improvements in other markers of metabolic health, which we did not detect in our study participants.”
 
The researchers involved in this study will continue to evaluate NMN’s metabolic effect on another trial which will involve men as well as women.