Wallis, G. A. | Search bioRxiv

bioRxiv2020

Nicotinamide Riboside supplementation does not alter whole-body or skeletal muscle metabolic responses to a single bout of endurance exercise

Oral supplementation of the NAD+ precursor Nicotinamide Riboside (NR) has been reported to increase Sirtuin (SIRT) signalling, mitochondrial biogenesis and endurance capacity in rodent skeletal muscle. However, whether NR supplementation can elicit a similar response in human skeletal muscle is unclear. This study aimed to assess the effect of 7-day NR supplementation on exercise-induced transduction and transcriptional responses in skeletal muscle of young, healthy, recreationally active human volunteers. In a double-blinded, randomised, counter-balanced, crossover design, eight male participants (age: 23 ± 4 years, VO2peak: 46.5 ± 4.4 mL·kg-1·min-1) received one week of NR or cellulose placebo (PLA) supplementation (1000 mg·d-1) before performing one hour of cycling at 60% Wmax. Muscle biopsies were collected prior to supplementation and pre-, immediately and three-hours post-exercise from the medial vastus lateralis, whilst venous blood samples were collected throughout the trial. Global acetylation, auto-PARylation of PARP1, acetylation of p53Lys382 and MnSODLys122 were unaffected by NR supplementation or exercise. Exercise led to an increase in AMPKThr172 (1.6-fold), and ACCSer79 (4-fold) phosphorylation, in addition to an increase in PGC-1α (∼5-fold) and PDK4 (∼10-fold) mRNA expression, however NR had no additional effect on this response. There was also no effect of NR supplementation on substrate utilisation at rest or during exercise or on skeletal muscle mitochondrial respiration. Finally, NR supplementation blunted the exercise induced activation of skeletal muscle NNMT mRNA expression, but had no effect on mRNA expression of NMRK1, NAMPT or NMNAT1, which were not significantly affected by NR supplementation or exercise. In summary, one week of NR supplementation does not augment skeletal muscle signal transduction pathways implicated in mitochondrial adaptation to endurance exercise.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2019

The Ufm1 system is upregulated by ER stress during osteogenic differentiation

ObjectiveMutations in the catalytic site of the ubiquitin-fold modifier 1(UFM1)-specific peptidase 2 (UFSP2) gene have been identified to cause autosomal dominant Beukes hip dysplasia in a large multigenerational family and a novel form of autosomal dominant spondyloepimetaphyseal dysplasia in a second family. We investigated the expression of the UFSP2/UFM1 system during mouse joint development the connection to ER stress induced during osteogenic differentiation.\n\nMethodsThe pattern of expression of Ufsp2 was determined by radioactive RNA in situ hybridisation on mouse tissue sections. qPCR was used to monitor expression during in vitro osteogenic differentiation and chemically induced ER stress. Affinity purification and mass spectrometry was used for isolation and identification of Ufm1 conjugation targets. Luciferase reporter assay was used to investigate the activity of Ufm1 system genes promoters.\n\nResultsWe found that Ufsp2 was predominantly expressed in the bone and secondary ossification centres of 10-day old mice. The Ufm1 system was upregulated during in vitro osteogenic differentiation and in response to chemically induced ER stress. We identified unfolded protein response elements in the upstream sequences of Uba5, Ufl1, Ufm1and Lzap. We identified putative Ufm1 conjugation targets where conjugation was increased in response to ER stress.\n\nConclusionHigher expression of Ufsp2 in bone and secondary ossification centres as well as upregulation of components of the Ufm1system in response to ER stress suggests that the molecular pathway between the UFSP2 mutations and form of skeletal dysplasia may relate to abnormal ER stress responses during osteoblast differentiation.

cell biology↗