Role of endothelial NAD deficiency in age-related vascular dysfunction.

Age-related alterations in endothelium and the resulting vascular dysfunction critically contribute to a range of pathological conditions associated with old age. To develop therapies rationally that improve vascular health and thereby increase health span and life span in older adults, it will be essential to understand the cellular and molecular mechanisms contributing to vascular aging. Preclinical studies in model organisms demonstrate that NAD availability decreases with age in multiple tissues and that supplemental NAD precursors can ameliorate many age-related cellular impairments. Here, we provide a comprehensive overview of NAD-dependent pathways [including the NAD-using silent information regulator-2-like enzymes and poly(ADP-ribose) polymerase enzymes] and the potential consequences of endothelial NAD deficiency in vascular aging. The multifaceted vasoprotective effects of treatments that reverse the age-related decline in cellular NAD levels, as well as their potential limitations, are discussed. The preventive and therapeutic potential of NAD intermediates as effective, clinically relevant interventions in older adults at risk for ischemic heart disease, vascular cognitive impairment, and other common geriatric conditions and diseases that involve vascular pathologies (e.g., sarcopenia, frailty) are critically discussed. We propose that NAD precursors [e.g., nicotinamide (Nam) riboside, Nam mononucleotide, niacin] should be considered as critical components of combination therapies to slow the vascular aging process and increase cardiovascular health span.