CD38 inhibitor 78c increases mice lifespan and healthspan in a model of chronological aging

Abstract Nicotinamide adenine dinucleotide (NAD) levels decline during aging, contributing to physical and metabolic dysfunction. The NADase CD38 plays a key role in age‐related NAD decline. Whether the inhibition of CD38 increases lifespan is not known. Here, we show that the CD38 inhibitor 78c increases lifespan and healthspan of naturally aged mice. In addition to a 10% increase in median survival, 78c improved exercise performance, endurance, and metabolic function in mice. The effects of 78c were different between sexes. Our study is the first to investigate the effect of CD38 inhibition in naturally aged animals.

aging, CD38, healthspan, longevity, mice, NAD, small molecule NAD is a cofactor of oxidation-reduction reactions and is a substrate for enzymes involved in cellular homeostasis (Chini et al., 2020;Hogan et al., 2019;Johnson & Imai, 2018;Katsyuba et al., 2020;McReynolds et al., 2020). NAD levels decrease with aging and progeroid states, which is associated with metabolic abnormalities and fitness decline (Camacho-Pereira et al., 2016;Gomes et al., 2013;Tarrago et al., 2018). The NAD-consuming enzymes such as CD38 and PARP1 have been shown to play a major role in this process (Aksoy et al., 2006;Camacho-Pereira et al., 2016;Tarrago et al., 2018). The accumulation of CD38 + -inflammatory cells decreases NAD levels in aging (Chini et al., , 2020Covarrubias et al., 2021). The small molecule 78c is a specific and potent inhibitor of CD38 (Chini et al., 2018;Escande et al., 2013;Tarrago et al., 2018) that boosts NAD levels, improves survival of progeroid mice, and ameliorates several metabolic, structural, and molecular features of aging (Tarrago et al., 2018). However, to date the effect of CD38 inhibition on natural aging and longevity has not been explored. Here, we demonstrate that 78c increases the lifespan and healthspan of naturally aged male mice.
When offered the food to young mice ad libitum, 78c significantly boosted NAD, validating the 78c PO treatment. ( Figure S1a).
We then placed 1-year-old C57BL/6 male and female mice on either a control or 78c diet and closely followed their healthspan and longevity ( Figure 1a).
When both sexes were grouped, treatment with 78c significantly improved longevity, with a maximal survival increase of 9% (p = 0.029) (Figure 1b). When analyzing survival for males and females separately, a sex-specific effect of 78c was observed. The 78c-treated males had a 17% increase in median survival (p = 0.008) and a 14% increase in maximal lifespan (p = 0.041) compared with control. (Figure 1c). In females, no significant survival benefit was observed ( Figure 1c).
The causes of death were classified as natural (i.e., animal found dead for unknown reason) and IACUC humane endpoint criteria ( Figure S1b). The latter encompasses not only moribund animals but also conditions of non-fatal health decline that elicit animal suffering. We observed a much higher proportion of IACUC criteria deaths in the 78c-treated females. Notably, the abrupt decline in the survival curve of that group coincides with the occurrence of consecutive euthanasias due to IACUC recommendation, suggesting that 78c may cause non-fatal deleterious conditions in female mice. ( Figure S1c). Interestingly, the survival analysis up to this point was statistically significant (Figure 1d). In addition, autopsy studies showed no significant difference in the proportion of visible tumors between treated and non-treated animals ( Figure   S1d), indicating that 78c increased longevity in males without an evident antitumor effect. presented a significant higher VO 2 , VCO 2 , and metabolic rate during the night fasting. There was a trend to increase in these same parameters during the day fasting and feed times (Figure 1j).
Body composition analysis showed that the 78c-treated animals presented a significant lower percentage of fat and higher lean mass compared to control (Figure 2a), which was not associated with caloric restriction ( Figure S1f). Females on 78c showed no significant difference in energy expenditure compared with control ( Figure S1g).
Especially during the night, 78c treatment significantly increased activity, ambulation, and rearing counts (Figure 2b), but rotarod performance showed no statistically significant differences (Figure 2c).
The control group presented an abrupt decline in their weight with aging, which is one indication of frailty. By contrast, the 78c-treated animals had a steadier variation in the weight curve throughout the whole experiment (Figure 2d).
We then evaluated the effect of 78c on the frailty in a cohort of old male mice (Figure 2e). Frailty scores were derived from clinical examination (Whitehead et al., 2014). Changes in frailty index after 3 months were plotted in comparison with the baseline index ( Figure 2f). All animals in the control group had a significantly higher frailty index than that was 3 months earlier, which occurred mainly due to a worsening in grimace, body condition score, kyphosis, tremor, and eye discharge. By contrast, 78c showed a pro- Our results represent the first in vivo longitudinal study using a CD38 inhibitor in natural aging. Oral administration of 78c allows a steady dose delivery, avoiding potential complications related to intraperitoneal injections. Therefore, this approach improves the translational potential of CD38 inhibitors as a therapy for agerelated diseases, promoting healthier aging. o. Graphs show VO 2 , VCO 2 , metabolic rate, REE, AEE, and TEE during periods of day and night, and feed and fast (n = 8 mice/group). Survival curves were analyzed with log-rank test. All other data are mean ± SEM and analyzed by unpaired two-sided t-test, *p < 0.05, **p < 0.01, ***p < 0.001