Researchers find ways to boost the energy supply of aging cells in an effort to stave off the detrimental effects of the inevitable passage of time.

‘Researchers have identified a protein responsible for transporting NMN directly into cells, where it can be used for cellular fuel production. Not only does this protein move NMN into cells, it does so rapidly.’

A key element of any cell's fuel supply chain is a molecule called nicotinamide adenine dinucleotide (NAD). Past work has shown that NAD levels in tissues throughout the body decrease with age. One way cells manufacture NAD begins with a precursor molecule called nicotinamide mononucleotide (NMN), which is found naturally in foods such as edamame, broccoli, cabbage, cucumber and avocado. But how NMN gets into cells to be processed into NAD has long been a mystery. 




The study is published in the inaugural issue of the journal Nature Metabolism.
Imai and his team long suspected there was a direct route for NMN to get into cells, simply because they had measured the speed with which NMN made the journey from the gut into the bloodstream and then into tissues throughout the body. In mice, that journey happens in a matter of minutes. The researchers felt there wasn't time for complex biochemical reactions that might convert NMN into another form that could be taken up by cells.
"To achieve such fast uptake of NMN into the tissues, we speculated that there must be a specific NMN transporter that moves NMN directly into cells, even though no one had ever seen such a thing," Imai said.
The researchers, led by first author Alessia Grozio, PhD, a staff scientist in developmental biology, conducted multiple experiments in cells and mice, identifying and then verifying that a protein called Slc12a8 is in fact the mystery transporter. The researchers also showed that Slc12a8 requires the presence of sodium ions to transport NMN into cells.
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Imai and Grozio pointed to the importance of the interaction of NMN and its transporter. It may not be enough, for example, to give NMN if the transporter is not working well. They see a role for both supplementing NMN and enhancing the function of Slc12a8 -- the NMN transporter -- in therapies that might help maintain cellular energy levels with age.
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"What may be important in a future strategy is the combination of giving NMN along with stimulating the transport of NMN into cells," Imai said. "With aging, we see a bottleneck in NAD production. The body loses its ability to manufacture NAD over time. At the same time, it seems to begin burning more NAD, likely due to chronic inflammation. If we can give NMN and aid its transport into cells, that may be a way to bypass the bottleneck."
With this in mind, Imai's lab already has identified small molecules that enhance the function of the NMN transporter. Working with Washington University's Office of Technology Management, this technology has been licensed to a company in Japan called Teijin Limited that is working on new therapies targeting the chronic diseases of aging. There also is an ongoing clinical trial at the School of Medicine investigating the effects of NMN on older adults.
Source-Eurekalert