Nicotinamide Riboside on Mitochondrial Function in Li-Fraumeni Syndrome

We have previously reported that inherited mutations of TP53, which causes the premature cancer disorder Li-Fraumeni syndrome (LFS), can promote mitochondrial function both in patients and mouse models. In the course of our follow up studies, we encountered a LFS patient with a long-standing history of fatigue and muscle weakness of unclear etiology. Notably, we observed in vivo evidence of markedly decreased mitochondrial function in her leg skeletal muscle during exercise using noninvasive phosphorus-31 magnetic resonance spectroscopy (31P-MRS), a technique that has previously been used to study patients with primary mitochondrial disorders. The decrease in mitochondrial function was also confirmed by the patient s skin fibroblasts in vitro using standard biochemical measurements.

There is growing evidence that nicotinamide adenine dinucleotide (NAD+) homeostasis plays a significant role in maintaining the mitochondria through various mechanisms and that it is possible to improve mitochondrial function by dietary supplementation with the vitamin B3 analogue nicotinamide riboside (NR), an intermediate in the NAD+ salvage pathway. Remarkably, we observed that culturing the LFS patient s fibroblasts in medium containing NR rescued the severe deficit in mitochondrial respiration. While continuing our investigations into the molecular mechanism(s) underlying the mitochondrial dysfunction observed in this patient, the in vitro rescue of the respiratory deficiency by NR presents a unique opportunity to investigate whether it can also be observed in vivo using skeletal muscle 31P-MRS. We propose to explore the effect of NR, currently available as a dietary supplement, on in vivo mitochondrial function in this LFS patient.