In addition to PARP and NAMPT, other NAD+ homeostasis factors such as sirtuins and CD38 also play important roles in cancers and other metabolic diseases, which have been extensively discussed in recent reviews (Yaku et al., 2018; Yoshino et al., 2018; Heske, 2019; Konen et al., 2019; Okabe et al., 2019; Navas and Carnero, 2021). The gene discussed is PARP1; the disease is cancer.