In contrast, no increase in the expression of NAD+ consuming enzymes such as CD38 (Fig. 6e, f), PARPs (Supplementary Fig. 4e) or sirtuins (Supplementary Fig. 4f) was observed, suggesting that reduced NAD+ levels in human sarcopenia primarily result from inability to synthesize and recycle NAD+. The gene discussed is CD38; the disease is sarcopenia.