Abstract
The paper delves into the critical role of NAD+ and its precursor, niacin, in health, aging, and disease management. It highlights the decline in NAD+ levels with aging, associated with age-related diseases, and the potential therapeutic benefits of restoring NAD+ through precursors like niacin. Boosting NAD+ levels have shown significant improvements in cardiovascular health by reducing blood pressure and arterial stiffness. Moreover, niacin supplementation exhibits anti-inflammatory effects and plays a crucial role in neurological health conditions like Alzheimer's and Parkinson's diseases. Studies also suggest that niacin may have a preventive effect on cancer and contribute to longevity by enhancing immune function and metabolic homeostasis. Overall, the research underscores the pivotal impact of NAD+ and niacin on well-being, longevity, and disease prevention, emphasizing the need for further exploration into targeted strategies for maintaining NAD+ availability through supplementation with its precursors including niacin.NAD+ levels decline with aging
NAD+ decline is a key feature of aging and cancer, and its restoration through precursors may offer therapeutic benefits (Demarest 2019, Khaidizar 2021). NAD+ levels decline with aging, a phenomenon attributed to increased consumption by NAD+-consuming enzymes such as PARPs, SARM1, sirtuins, and CD38 (Schultz 2016, Strømland 2021). This decline has been observed in various species, including humans, and is associated with age-related diseases (Peluso 2021, Clement 2019). The decline in NAD+ levels is accompanied by an increase in the reduced form of NAD+ and NADP+ (Clement 2019). This age-related decline in NAD+ levels is linked to metabolic dysfunction and age-related diseases (Chini 2017). However, the evidence for this decline is limited and often restricted to a single tissue or cell type (Peluso 2021). Further research is needed to better understand the role of NAD+ in aging and to develop targeted strategies to maintain its availability (McReynolds 2020).Boosting NAD+ levels improve cardiovascular health
A growing body of research suggests that boosting NAD+ levels can improve cardiovascular health. Chronic supplementation with NAD+ precursors, such as nicotinamide riboside, is well-tolerated and effectively elevates NAD+ levels in healthy middle-aged and older adults, potentially reducing blood pressure and arterial stiffness (Martens 2018, Rotllan 2021, Freeberg 2023). NAD+ precursors are safe and can increase NAD+ levels in multiple tissues (Freeberg 2023). Boosting NAD+ metabolism in cardiovascular diseases has the potential benefits (Matasic 2018). NAD+ repletion can induce health benefits in age-related cardiovascular and metabolic disease models (Kane 2018). The positive effects of NAD+ replenishment in preclinical models of cardiovascular diseases were noted (Abdellatif 2021), including the potential of nicotinamide mononucleotide as a nutraceutical against cardiac aging (Wei 2021). Mechanistic evidence, showing that boosting NAD+ levels can improve mitochondrial respiration and reduce proinflammatory activation in heart failure patients was shown (Zhou 2020).NAD precursors and hallmarks of aging
NAD+ is a critical metabolite that declines with aging and is associated with age-related diseases (Lautrup 2023). Its depletion contributes to mitochondrial dysfunction, a hallmark of aging (McReynolds 2019). NAD+ precursors, such as niacin, nicotinamide riboside and nicotinamide mononucleotide, have shown potential in promoting healthy aging and improving neurodegeneration (Reiten 2021). These precursors have also been linked to lifespan extension and redox homeostasis (Lin 2015, Braidy 2019). Boosting NAD+ levels may counter aging-associated pathologies and age-related diseases (Aman 2018). The NAD+-mitophagy axis, which regulates mitochondrial homeostasis, is a promising therapeutic target for aging and neurodegenerative diseases (Aman 2018). NAD+ precursors have been shown to improve glucose and lipid metabolism, reduce weight gain, and protect the heart from ischemic injury (Bhasin 2023). Age-related changes in NAD+ metabolism in the brain have been linked to Alzheimer's disease (Braidy 2010).Comparison of NAD+ Precursors in Biological and Therapeutic Effects
NAD+ precursors, including niacin, niacinamide (NAM), and NMN, play crucial roles in cellular processes and have garnered attention for their therapeutic potential. Here is a comparison of these precursors based on their biological effects and FDA approval status:- Niacin (NA):
- Niacin has been established as an approved drug for the treatment of certain conditions (Yaku 2023).
- It is known for its role in redox reactions and as a signaling molecule that controls key processes like energy metabolism and cell survival (Rajman 2018).
- Niacin has been shown to delay the onset of diabetes mellitus type 1 in experimental models and prevent inflammation and atherosclerosis in animals (Rotllan 2021).
- Niacinamide (NAM):
- Niacinamide has demonstrated neuroprotective effects and reduced infarct size in experimental models (Rajman 2018).
- Studies have shown that NAM administration did not cause adverse effects and prevented inflammation and atherosclerosis in animals (Rotllan 2021).
- Nicotinamide Mononucleotide (NMN):
- NMN has shown promising therapeutic effects, including reducing infarct size in experimental models (Rajman 2018).
- Recent evidence suggests that NMN treatment replicated the neuroprotective effects seen with NAM administration (Rajman 2018).
Comparison of niacin and NAM, NMN on lipid metabolism
Niacin and its derivatives, such as NAM and NMN, have shown effects on reducing LDL-cholesterol and increasing HDL-cholesterol levels. Niacin, in pharmacological doses, acts as a lipid-modulating drug that increases HDL levels, which are crucial for cholesterol scavenging and transport to the liver (Rajman 2018). It has been found to reduce non-HDL cholesterol levels and cardiovascular events (Rajman 2018). Niacin also plays a role in stabilizing ApoA-I and preventing the uptake of HDL in the liver, thereby increasing HDL availability for cholesterol scavenging (Rajman 2018). On the other hand, NAM supplementation has shown significant effects on improving lipid metabolism, particularly in patients with cardiovascular disease and dyslipidemia (Zhong 2022). While NAM itself may not directly improve lipid metabolism, it is essential in the NAD+ pathway, which influences lipid levels. NMN, another precursor, has been linked to improving muscle performance and increasing NAM levels in the body (Pirinen 2020). In summary, niacin has a direct impact on lipid metabolism by increasing HDL levels and reducing non-HDL cholesterol, while NAM and NMN play roles in the NAD+ pathway that indirectly affect lipid metabolism. Each of these compounds offers unique benefits in managing cholesterol levels.Advantages of Niacin Over NAM and NMN
Niacin, a well-known NAD+ precursor, offers distinct advantages over nicotinamide (NAM) and nicotinamide mononucleotide (NMN) based on various studies and research findings:- Metabolic Bypass Therapy:
- Niacin serves as a metabolic "by-pass" therapy, providing functional benefits through the suppression of mTOR signaling (Pirinen 2020).
- This unique characteristic of niacin highlights its potential in metabolic regulation and cellular processes.
- Approved Drug Status:
- Niacin has been established as an approved drug for specific therapeutic applications (Yaku 2023).
- Its approval status signifies its recognized efficacy and safety profile in clinical settings.
- Lipid Modulation and Health Benefits:
- Niacin has been shown to increase the use of lipids as energy substrates, improve cholesterol profiles, and promote SIRT1-target gene expression in adipose tissues (Romani 2019).
- These lipid-modulating effects of niacin contribute to its potential benefits for cardiovascular health and metabolic functions.
Niacin supplementation improves cardiovascular health.
Niacin supplementation has been shown to improve cardiovascular health through various mechanisms. It inhibits acute vascular inflammation and improves endothelial function, independent of changes in plasma lipid levels (Wu 2010). It also improves the distribution of lipoprotein particle sizes and reduces inflammatory markers in patients with coronary artery disease (Kuvin 2006). Furthermore, niacin has been associated with a reduction in cardiovascular events, including coronary artery revascularization, nonfatal myocardial infarction, and stroke (Duggal 2010). However, the efficacy of niacin in reducing cardiovascular disease events has been challenged by the results of the AIM-HIGH trial (Lavigne 2013. Despite these conflicting findings, niacin has consistently shown benefits in preventing or treating atherosclerotic cardiovascular disease in various clinical trials (Guyton 1998). However, the role of niacin in managing cardiovascular disease outcomes in current practice remains uncertain (D'Andrea 2019, Garg 2017).Niacin and inflammation
Niacin supplementation has been shown to have anti-inflammatory effects in various studies. Niacin was found to reduce oxidative stress and inflammation in rats with chronic renal failure (Cho 2009), to inhibit acute vascular inflammation and improved endothelial function (Wu 2010, Wu 2012), to alter lipoprotein particle size and distribution, and to reduce inflammatory markers in patients with coronary artery disease (Kuvin 2006). Niacin increased anti-inflammatory markers and decreased pro-inflammatory markers in mice with high-fat diet-induced obesity and rats with ulcerative colitis, respectively (Wanders 2013, Salem 2017). These findings were further supported by the findings that show that niacin downregulated the nuclear transcription factor-κB signaling pathway and attenuated lung inflammation in guinea pigs and rats with sepsis (Si 2014, Kwon 2011).Niacin improves renal insufficiency
Niacin supplementation has shown promising results in ameliorating oxidative stress, inflammation, proteinuria, and hypertension in rats with chronic renal failure (Cho 2009). It has also been found to improve renal lipid metabolism and slow the progression of chronic kidney disease (Cho 2009b). Furthermore, niacin has been suggested as a potential treatment for dyslipidemia and hyperphosphatemia associated with chronic renal failure (Ahmed 2010). In patients with chronic kidney disease, low-dose niacin supplementation has been found to improve dyslipidemia, lower serum phosphorus levels, and increase glomerular filtration rate (Kang 2013). McConnell and Penberthy (McConnell 2021) reported improvement or reversal of renal insufficiency in more than 2 dozen patients with various stages of renal insufficiency by taking niacin along with sodium bicarbonate.Niacin's effects on neurological health
Niacin plays a crucial role in neurological health, particularly in conditions like Alzheimer's disease (AD), Parkinson's disease (PD), emotional disorders, and schizophrenia.- 1. Alzheimer's Disease.
- Association with AD: Dietary niacin intake has been inversely associated with AD, suggesting a potential protective effect against cognitive decline (Gasperi 2019).
- Biological Mechanisms: Niacin influences key biological processes like energy metabolism, mitochondrial functions, and calcium homeostasis, which are vital for brain functions such as neurotransmission, learning, and memory (Gasperi 2019).
- Clinical Trials: Studies have shown that niacin supplementation may help limit Alzheimer's progression by modulating microglial activity in the brain (Manjarrez 2022).
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Parkinson's Disease
- Niacin's Role: Increased niacin intake enhances striatal dopamine synthesis and restores optimal NAD+/NADH ratio in PD patients (Gasperi 2019).
- Clinical Trials: Research suggests that niacin enhancement can potentially maintain or improve quality of life in PD patients and slow disease progression (Chong 2021).
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Emotional Disorders and Schizophrenia
- Symptom Management: Niacin supplementation has been shown to combat symptoms like psychosis, disorientation, memory loss, and confusion in conditions resembling AD (Fricker 2018).
- Neuro-Inflammation: Niacin has been found to ameliorate neuro-inflammation in PD through specific receptors like GPR10 (Fricker 2018).