Low NAD+ Levels Are Associated With a Decline of Spermatogenesis in Transgenic ANDY and Aging Mice.

Frontiers in endocrinology 2022

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Advanced paternal age has increasingly been recognized as a risk factor for male fertility and progeny health. While underlying causes are not well understood, aging is associated with a continuous decline of blood and tissue NAD+ levels, as well as a decline of testicular functions. The important basic question to what extent ageing-related NAD+ decline is functionally linked to decreased male fertility has been difficult to address due to the pleiotropic effects of aging, and the lack of a suitable animal model in which NAD+ levels can be lowered experimentally in chronologically young adult males. We therefore developed a transgenic mouse model of acquired niacin dependency (ANDY), in which NAD+ levels can be experimentally lowered using a niacin-deficient, chemically defined diet. Using ANDY mice, this report demonstrates for the first time that decreasing body-wide NAD+ levels in young adult mice, including in the testes, to levels that match or exceed the natural NAD+ decline observed in old mice, results in the disruption of spermatogenesis with small testis sizes and reduced sperm counts. ANDY mice are dependent on dietary vitamin B3 (niacin) for NAD+ synthesis, similar to humans. NAD+-deficiency the animals develop on a niacin-free diet is reversed by niacin supplementation. Providing niacin to NAD+-depleted ANDY mice fully rescued spermatogenesis and restored normal testis weight in the animals. The results suggest that NAD+ is important for proper spermatogenesis and that its declining levels during aging are functionally linked to declining spermatogenesis and male fertility. Functions of NAD+ in retinoic acid synthesis, which is an essential testicular signaling pathway regulating spermatogonial proliferation and differentiation, may offer a plausible mechanism for the hypospermatogenesis observed in NAD+-deficient mice. Copyright © 2022 Meyer-Ficca, Zwerdling, Swanson, Tucker, Lopez, Wandersee, Warner, Thompson, Chini, Chen, Chini and Meyer.

Citation

Mirella L Meyer-Ficca, Alexie E Zwerdling, Corey A Swanson, Abby G Tucker, Sierra A Lopez, Miles K Wandersee, Gina M Warner, Katie L Thompson, Claudia C S Chini, Haolin Chen, Eduardo N Chini, Ralph G Meyer. Low NAD+ Levels Are Associated With a Decline of Spermatogenesis in Transgenic ANDY and Aging Mice. Frontiers in endocrinology. 2022;13:896356