NAD depletion in skeletal muscle does not compromise muscle function or accelerate aging

Area of Science:

• Biochemistry
• Cellular Biology
• Aging Research

Background:

• Nicotinamide adenine dinucleotide (NAD) is crucial for cellular energy metabolism and protein regulation.
• NAD depletion is often linked to aging, but the threshold for adverse effects is unknown.
• Skeletal muscle NAD+ biosynthesis is primarily mediated by NAMPT.

Purpose of the Study:

• To investigate the functional consequences of significant NAD+ depletion in adult skeletal muscle.
• To determine if reduced NAD+ levels contribute to age-related muscle dysfunction.
• To assess the impact of lifelong NAD+ depletion on overall health and metabolism.

Main Methods:

• Generated a mouse model with disrupted NAMPT-mediated NAD+ biosynthesis in adult skeletal muscle.
• Quantified NAD+ reduction and assessed muscle morphology, contractility, and exercise tolerance.
• Analyzed mitochondrial respiration, muscle transcriptomics, and proteomics.

Main Results:

• Achieved an 85% reduction in muscle NAD+ without compromising tissue integrity or function.
• Observed preserved muscle morphology, contractility, and exercise capacity.
• Found intact mitochondrial function and unaltered molecular profiles; no accelerated aging or metabolic impairment.

Conclusions:

• Significant NAD+ depletion in adult skeletal muscle does not lead to functional deficits.
• NAD+ levels may not be a primary determinant of age-related skeletal muscle decline.
• These findings challenge the direct link between NAD+ depletion and age-associated muscle aging.