NAD+

BACKGROUND: Hyperuricemia (HUA) involves multi-organ dysfunction, particularly hepatic and renal abnormalities. Danggui-Niantong decoction (DGN) is a traditional formula for gout and chronic kidney disease. Clinically, DGN is often combined with drugs that regulate hepatic function to treat HUA. Anoectochilus roxburghii (AR) is recognized for its hepatoprotective properties. However, whether the AR and DGN combination (AR+DGN) exerts superior urate-lowering and organ-protective effects compared to monotherapy, and the mechanisms underlying this combined treatment, remain unclear. PURPOSE: This study aimed to evaluate the therapeutic efficacy of AR, DGN, and AR+DGN in hyperuricemic rats, and to investigate the mechanisms of this combined action via integrated gut microbiota and metabolomics analyses. METHODS: First, the active components and fingerprints of AR and DGN were characterized using UPLC-MS and HPLC. A hyperuricemic model was established in male Sprague-Dawley rats via a high-purine diet. Following a preliminary experiment to determine the optimal AR dose (n = 30), 48 rats were randomized into six groups (n = 8): Control, HUA, Benzbromarone (Ben), AR, DGN, and AR+DGN. After 4 weeks of intragastric administration, therapeutic efficacy was assessed via serum uric acid (SUA), hepatorenal function markers, and histopathology. Subsequently, 16S rRNA sequencing and untargeted metabolomics were employed to screen potential signaling pathways, which were further validated by western blot, immunofluorescence, and RT-qPCR. RESULTS: A total of 296 compounds were identified collectively across the AR and DGN extracts, and ten bioactive markers, including kinsenoside, chlorogenic acid, and isoimperatorin, were rigorously quantified for quality standardization. Compared to monotherapy, AR+DGN provided dual protection by restoring both hepatic and renal functions and demonstrated a superior urate-lowering capacity, reducing SUA levels by 58.2% and serum alanine aminotransferase levels by 59.6% compared to the HUA group (p < 0.01), while maintaining normal liver enzyme levels unlike benzbromarone. Mechanistically, AR+DGN restored gut microbiota dysbiosis in hyperuricemic rats, notably enriching seven beneficial genera (e.g., Alistipes and Bifidobacterium) while depleting four pathogenic genera (e.g., Escherichia-Shigella and Coriobacteriaceae_UCG_002). Furthermore, elevated levels of beta-nicotinamide mononucleotide, propionate, butyrate, and isobutyrate, along with reduced inosine and xanthine, were identified as key metabolites significantly associated with these microbial alterations (p < 0.05). KEGG analysis identified NAD+ metabolism and purine metabolism as key pathways co-regulated in both serum and intestinal contents. Critically, AR+DGN upregulated hepatic NAD+ biosynthetic enzymes (QPRT, NMNAT3, and NAMPT by 1.74-, 2.64-, and 1.79-fold, respectively), thereby boosting liver and serum NAD+ levels. This metabolic restoration, coupled with a 62.5% reduction in hepatic reactive oxygen species, indicated the disruption of the uric acid-oxidative stress positive feedback loop. Simultaneously, AR+DGN restored renal urate transport balance by inhibiting reabsorptive transporters (GLUT9, URAT1) while upregulating the secretory transporter (ABCG2), ultimately contributing to the significant urate-lowering efficacy. CONCLUSIONS: This study demonstrates that AR+DGN exerts superior urate-lowering efficacy and hepatorenal protection. Mechanistically, it functions by remodeling the gut microbiota-metabolic axis to regulate hepatic NAD+ metabolism and renal urate transport, supporting its potential for the safe and long-term management of HUA.

Glaucoma and age-related macular degeneration (AMD) are progressive retinal diseases characterized by increased oxidative stress, inflammation, and mitochondrial dysfunction. This review investigates the potential therapeutic benefits of NAD+ and niacin supplementation in managing glaucoma and AMD. A literature search was conducted encompassing keywords such as "niacin", "NAD", "glaucoma", "AMD", and "therapeutics". NAD+ depletion is associated with increased oxidative stress and mitochondrial dysfunction in glaucoma and AMD. Niacin, a precursor to NAD+, has shown promise in replenishing NAD+ levels, improving choroidal blood flow, and reducing oxidative damage. Animal studies in glaucoma models indicate that nicotinamide (NAM) supplementation preserves RGC density and function. Large-scale population-based studies indicate an inverse correlation between niacin intake and glaucoma prevalence, suggesting a preventative role. Randomized controlled trials assessing niacin supplementation showed significant improvements in visual field sensitivity and inner retinal function, with a dose-dependent relationship. In AMD, nicotinamide supplementation may improve rod cell function and protect against oxidative stress-induced damage. Cross-sectional studies reveal that individuals with AMD have a lower dietary intake of niacin. Further studies suggest niacin's role in improving choroidal blood flow and dilating retinal arterioles, potentially mitigating ischemic damage and oxidative stress in AMD. Beyond current management strategies, NAD+ and niacin supplementation may offer novel therapeutic avenues for glaucoma and AMD. Further research is warranted to elucidate their efficacy and safety in clinical settings.

Beyond their classical functions as redox cofactors, recent fundamental and clinical research has expanded our understanding of the diverse roles of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) in signaling pathways, epigenetic regulation and energy homeostasis. Moreover, NAD and NADP influence numerous diseases as well as the processes of aging, and are emerging as targets for clinical intervention. Here, we summarize safety, bioavailability and efficacy data from NAD+-related clinical trials, focusing on aging and neurodegenerative diseases. We discuss the established NAD+ precursors nicotinic acid and nicotinamide, newer compounds such as nicotinamide riboside and nicotinamide mononucleotide, and emerging precursors. We also discuss technological advances including in industrial-scale production and real-time detection, which are facilitating NAD+ research and clinical translation. Finally, we emphasize the need for further large-scale studies to determine optimal dose, administration routes and frequency, as well as long-term safety and interindividual variability in response.

BACKGROUND: Long-COVID often involves cognitive difficulties, immune dysregulation, and mitochondrial dysfunction. Studies suggest nicotinamide adenine dinucleotide (NAD+) precursors like nicotinamide riboside (NR) may reduce inflammation and support mitochondrial and neurological function. This double-blind, placebo (PBO)-controlled clinical trial with a placebo lead-in phase evaluated the effects of NR (2000 mg/day) on NAD+ and changes in cognitive and long-COVID symptoms. METHODS: This was a 24-week, double-blind, placebo-controlled trial at a single center in Boston, USA, between August 2021 and September 2023. 58 community-dwelling participants with long-COVID were randomized 2:1 to the NR-NR group (NR for 20 weeks) or the PBO-NR group (PBO for 10 weeks, followed by NR for 10 weeks). The primary outcome was cognition, assessed using the Everyday Cognition scale (ECog), Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and Trail Making Test-B (TMT-B). Secondary outcomes included the Fatigue Severity Scale (FSS), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), and Pittsburgh Sleep Quality Index. We conducted a mixed model for repeated measures to compare groups, then post-hoc and unadjusted for multiplicity, combined both groups to explore changes from baseline after 10 weeks of NR. This trial was registered with ClinicalTrials.gov (NCT04809974) in 2021. FINDINGS: 37 participants (64%) were assigned to NR-NR, and 21 participants (36%) to PBO-NR. There was a 32.4% and 51.4% dropout in the NR-NR group at 10 weeks and 20 weeks, respectively, vs. 14.3% dropout at each timepoint in the PBO-NR group. In the NR-NR group, NAD+ levels increased by 2.6- to 3.1-fold after 5-10 weeks of supplementation, respectively, and remained elevated at 20 weeks. In the PBO-NR group, NAD+ levels remained close to baseline (0.93- to 1.0-fold change, 95% CI: 0.5-1.4) during the initial 5 and 10 weeks of PBO. After switching to NR, levels rose to a 2.6-fold and 2.1-fold increase after 5 and 10 weeks of NR, respectively. No significant between-group differences were observed for cognitive outcomes (ECog, RBANS, TMT-B; p-values = 0.47-0.74). There were no significant differences in fatigue severity (p = 0.59), sleep quality p = 0.69), and symptoms of anxiety (p = 0.84) or depression (p = 0.20) between PBO and NR groups. In post-hoc exploratory analysis, examining within-group changes during 5 and 10 weeks of NR intake by grouping all participants during the first 10 weeks of the NR phase, there were significant differences from baseline after 10 weeks of NR in executive functioning, fatigue severity, sleep quality, and symptoms of depression (compared with no significant changes in TMT-B, FSS, PSQI, BAI, or BDI scores during the PBO phase). One serious adverse event was reported, deemed unrelated to the study drug or trial. INTERPRETATION: In long-COVID, NR increased NAD+ within 5 weeks but did not significantly improve cognition, fatigue, sleep, or mood vs. PBO. Exploratory analyses suggested within-group benefits after 10 weeks of NR, supporting the need for larger trials. FUNDING: This work was supported by Niagen Bioscience, the MGH McCance Center for Brain Health, Lavine Brain Health Innovation Fund, MGH ECOR CDI Physician-Scientist Development Award, and the Alzheimer's Association (grant no. AARGD-23-114103).

Age-related decline in mobility and cognition are associated with cellular senescence and NAD + depletion in dogs and people. A combination of a novel NAD + precursor and senolytic, LY-D6/2, was examined in this randomized controlled trial. Seventy dogs with mild to moderate cognitive impairment were enrolled and allocated into placebo, low or full dose groups. Primary outcomes were change in cognitive impairment measured with the owner-reported Canine Cognitive Dysfunction Rating (CCDR) scale and change in activity measured with physical activity monitors. Fifty-nine dogs completed evaluations at the 3-month primary endpoint, and 51 reached the 6-month secondary endpoint. There was a significant difference in CCDR score across treatment groups from baseline to the primary endpoint (p = 0.02) with the largest decrease in the full dose group. No difference was detected between groups using in house cognitive testing. There were no significant differences between groups in changes in measured activity. The proportion of dogs that improved in frailty and owner-reported activity levels and happiness was higher in the full dose group than other groups, however this difference was not significant. Adverse events occurred equally across groups. All groups showed improvement in cognition, frailty, and activity suggesting placebo effect and benefits of trial participation. We conclude that LY-D6/2 improves owner-assessed cognitive function over a 3-month period and may have broader, but more subtle effects on frailty, activity and happiness as reported by owners.

Declining nicotinamide adenine dinucleotide (NAD+ ) concentration in the brain during aging contributes to metabolic and cellular dysfunction and is implicated in the pathogenesis of aging-associated neurological disorders. Experimental therapies aimed at boosting brain NAD+ levels normalize several neurodegenerative phenotypes in animal models, motivating their clinical translation. Dietary intake of NAD+ precursors, such as nicotinamide riboside (NR), is a safe and effective avenue for augmenting NAD+ levels in peripheral tissues in humans, yet evidence supporting their ability to raise NAD+ levels in the brain or engage neurodegenerative disease pathways is lacking. Here, we studied biomarkers in plasma extracellular vesicles enriched for neuronal origin (NEVs) from 22 healthy older adults who participated in a randomized, placebo-controlled crossover trial (NCT02921659) of oral NR supplementation (500 mg, 2x /day, 6 weeks). We demonstrate that oral NR supplementation increases NAD+ levels in NEVs and decreases NEV levels of Aβ42, pJNK, and pERK1/2 (kinases involved in insulin resistance and neuroinflammatory pathways). In addition, changes in NAD(H) correlated with changes in canonical insulin-Akt signaling proteins and changes in pERK1/2 and pJNK. These findings support the ability of orally administered NR to augment neuronal NAD+ levels and modify biomarkers related to neurodegenerative pathology in humans. Furthermore, NEVs offer a new blood-based window into monitoring the physiologic response of NR in the brain.