Preclinical Characterization of Pharmacologic NAD⁺ Boosting as a Promising Therapeutic Approach in Rheumatoid Arthritis

Objective: We analyzed NAD⁺ metabolism in patients with rheumatoid arthritis (RA), its association with disease activity and clinical outcomes of RA, and the therapeutic potential of pharmacologic NAD⁺ boosting.

Methods: Our study included 253 participants. In the first cohort, comprising 153 RA patients and 56 healthy donors, we assessed NAD⁺ levels and NAD⁺ -related gene pathways. We analyzed 92 inflammatory molecules by proximity extension assay. In the second cohort, comprising 44 RA patients starting anti-tumor necrosis factor (anti-TNF) drugs, we evaluated changes in NAD⁺ levels and their association with clinical response after 3 months. Mechanistic studies were performed ex vivo on peripheral blood mononuclear cells (PBMCs) from patients with RA to test the beneficial effects of NAD⁺ boosters, such as nicotinamide and nicotinamide riboside.

Results: Reduced NAD⁺ levels were found in RA samples, in line with altered activity and expression of genes involved in NAD⁺ consumption (sirtuins, poly[ADP-ribose] polymerase, CD38), transport (connexin 43), and biosynthesis (NAMPT, NMNATs). Unsupervised clustering analysis identified a group of RA patients with the highest inflammatory profile, the lowest NAD⁺ levels, and the highest disease activity (as shown by the Disease Activity Score in 28 joints). NAD⁺ levels were modulated by anti-TNF therapy in parallel with the clinical response. In vitro studies using PBMCs from RA patients showed that nicotinamide riboside and nicotinamide increased NAD⁺ levels via NAMPT and NMNAT and reduced their prooxidative, proapoptotic, and proinflammatory status.

Conclusion: RA patients display altered NAD⁺ metabolism, directly linked to their inflammatory and disease activity status, which was reverted by anti-TNF therapy. The preclinical beneficial effects of NAD⁺ boosters, as shown in leukocytes from RA patients, along with their proven clinical safety, might pave the way for the development of clinical trials using these compounds.