Key Pointers
NAD+ impacts muscles in the following way;
- Helps in energy production for muscles.
- Supports muscle regeneration.
- Have a role in myogenesis.
As a component of the human body, NAD+ has two general functions, it does the metabolic work of turning food into energy and acts as a helper molecule for proteins to regulate their functions. Grasping, breathing, and moving are all facilitated by the skeletal muscle. Additionally, skeletal muscle plays an important role in metabolic, core temperature and immune functions. A significant component of glycolysis occurs in muscle tissue, which also consumes significant quantities of fatty acids. The hydrogen/electron transfer molecule NAD+ is required for fatty acid and glucose metabolism. NAD+ is therefore crucial to the production of energy. The skeletal muscles comprise hundreds of mitochondria. NAD+ is required for the aerobic metabolism of glucose that occurs in the cells.
ADP-ribosylation and deacetylation also occur with NAD+ as co-substrates. As a result, NAD+ levels have a significant impact on many cellular functions, particularly mitochondrial biogenesis, transcription, and cellular composition. NAD+ provides important benefits to disease, injury, and regeneration of the skeletal muscle.
NAD+ levels are negatively associated with muscle health when they are low, and higher NAD+ concentrations bolster muscle health when they are high. Metabolically, skeletal muscle plays an important role in posture and locomotion. During systemic, energy-demanding processes, such as temperature regulation and immunity, the skeletal muscle recognizes, produces, stores, and uses nutrients and energy transfer molecules. Muscles in the skeleton are flexible and easily adaptable to change. There are several ways that muscle builds up plasticity, including hypertrophy after load-bearing exercise, atrophy after disuse, and genetic expression, cellular metabolism, and membrane changes to account for the switch in muscle fiber type.
During cellular metabolism, nutrients metabolized from food are converted into molecules that fuel the cell, including adenosine triphosphate (ATP). The interpretation of energy is, therefore, one of the most crucial functions of cells. Both oxidized nicotinamide adenine dinucleotides (NAD+) and their reduced forms, reduced nicotinamide adenine dinucleotide (NADH), interact with tricarboxylic acid (TCA) to generate energy by undergoing oxidation-reduction reactions (redox).
It is hypothesized that NAD+ levels could be correlated with glucose nutrient-sensing, thus enabling nutrition and myogenesis to be coordinated. The level of NAMPT is modulated by energy-sensing, for instance. It is AMPK that promotes NAMPT activity, and glucose restriction increases AMPK activity. In the absence of glucose, thus, glucose restriction encourages increased NAD+ production and improved SIRT1 function. A modulation of NAD + levels in vivo is not required for primary (embryonic) myogenesis.
Data suggest, however, that secondary myogenesis (fetal) may involve information from nutrient sensing and SIRT1 activity to mediate muscle growth. A reduction in secondary myogenesis results in smaller rats born to calorie-restricted mothers.
These results suggest that nutrient availability via NAD+ plays a role in muscle differentiation and growth. Although there are still a few unanswered questions about the mechanisms that determine which signal transmission pathways are triggered by NAD+. Satellite cells located just below the basement membrane mediate muscle repair. When a muscle is injured, these cells become proliferating and differentiating. In satellite cells, SIRT1 may repress transcription of myogenic genes to maintain quiescence.
Conclusion
Muscles require enough amount of energy to perform their functions throughout the body. The NAD+ is responsible for the generation of energy used by these muscles. Another important interaction of NAD+ with muscle is regeneration and growth of muscle components.
References
- Glancy B, Hartnell LM, Malide D, Yu ZX, Combs CA, Connelly PS, et al. Mitochondrial reticulum for cellular energy distribution in muscle. Nature. 2015;523:617–620. doi: 10.1038/nature14614.
- Fulco M, Cen Y, Zhao P, Hoffman EP, McBurney MW, Sauve AA, et al. Glucose restriction inhibits skeletal myoblast differentiation by activating SIRT1 through AMPK-mediated regulation of Nampt. Dev Cell. 2008;14:661–673. doi: 10.1016/j.devcel.2008.02.004.
- Zolkiewska A, Moss J. Processing of ADP-ribosylated integrin alpha 7 in skeletal muscle myotubes. J Biol Chem. 1995;270:9227–9233. doi: 10.1074/jbc.270.16.9227.