Everything below concerns enzymatic cycling assay. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Cells produce NAD+ through several biosynthetic routes. The salvage pathway recycles nicotinamide, while the Preiss-Handler pathway uses nicotinic acid, and a de novo route can start from tryptophan in some organisms. In mammals, the salvage pathway is generally considered the main source under ordinary conditions. Tissue concentrations vary widely by cell type and compartment, and measured declines with age have been reported in some studies. Whether such changes drive aging or mainly accompany it remains an open question.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a coenzyme present in all living cells. The molecule consists of two nucleotides linked by phosphate groups, with adenine and a nicotinamide ring as its principal features. In its oxidized form, the nicotinamide ring can accept a hydride ion, becoming NADH. This reversible conversion places NAD+ at the center of many electron-transfer reactions. Its role as a redox carrier is well established across bacteria, plants, fungi, and animals.
Beyond redox chemistry, NAD+ is consumed as a substrate by enzymes that transfer ADP-ribose or remove acetyl groups. Sirtuins use NAD+ in deacylation reactions, poly(ADP-ribose) polymerases use it in DNA damage responses, and CD38 hydrolases convert it to signaling metabolites. Because these enzymes compete for the same pool, changes in NAD+ availability can influence multiple cellular processes. The relative contribution of each consumption route differs by cell type and condition, and precise quantitative links remain an active area of study.
Research on NAD+ spans biochemistry, aging biology, and metabolism. Studies often examine how NAD+ levels change with age, diet, exercise, or disease states, and whether precursor supplementation alters those levels. Findings in animal models do not automatically translate to humans, and measurement methods vary across studies. Questions about tissue-specific effects, long-term consequences, and causal relationships remain open. NAD+ itself is not established as a single therapeutic agent with a broad clinical role.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide composed of two nucleotides joined by phosphate groups. One nucleotide contains adenine; the other contains nicotinamide. The molecule exists in oxidized (NAD+) and reduced (NADH) forms, and the reversible hydride transfer between them underlies many metabolic oxidation-reduction reactions. In cells, NAD+ serves as an electron acceptor in pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation. Its concentration and redox ratio vary by compartment, tissue, and metabolic state.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C21H27N7O14P2 | Oxidized free acid form; charge depends on pH. |
| Molar mass | 663.43 g/mol | Calculated for the free acid. |
| CAS Registry Number | 53-84-9 | For the anhydrous free acid; salts have different identifiers. |
| Appearance | White to off-white powder | Solid material; hygroscopic. |
| Solubility | Water-soluble | Dissolves in aqueous buffers; solubility varies with pH and salt. |
Research on NAD+ often examines changes with age, diet, exercise, and disease states, but causal relationships are difficult to establish. Some studies measure NAD+ levels, while others assess enzyme activity or downstream markers. In the literature, terms such as "NAD+ decline" and "NAD+ boosting" appear in both scientific and commercial contexts, sometimes without precise definitions. Whether changes in measured NAD+ directly produce health effects remains an open question. Results from cells, animals, and humans cannot be assumed to translate directly.
Measuring NAD+ in biological samples requires rapid processing because the compound can degrade or interconvert after collection. Common approaches include enzymatic cycling assays, high-performance liquid chromatography, and mass spectrometry. Each method has different sensitivity, specificity, and susceptibility to interference from related nucleotides. Sample type matters: cultured cells, animal tissues, and human blood present distinct challenges. Reported values can vary widely across laboratories because of differences in extraction, normalization, and analytical platform. Standardization remains an open issue in the field.
Purified NAD+ is typically supplied as a white to off-white powder and stored desiccated at low temperature. Airtight containers limit moisture uptake, while protection from light reduces degradation of the nicotinamide ring. Aqueous stock solutions are less stable than solid material and are often aliquoted before freezing. Repeated freeze-thaw cycles can lower integrity, so working portions are kept separate. Purity is commonly checked by ultraviolet absorbance near 260 nm, high-performance liquid chromatography, or mass spectrometry.
Stability studies show that NAD+ can hydrolyze under prolonged heat, extreme pH, or microbial contamination. Phosphate buffers near neutral pH are often used for short-term handling, though exact stability depends on concentration, temperature, and matrix. In biological samples, endogenous enzymes can rapidly degrade NAD+, making cold chain and fast processing important. Analytical reports should state extraction conditions, internal standards, and validation parameters. Without those details, comparisons across studies remain difficult and potentially misleading.
Related compounds include NADH, the reduced form, and NADP+, which carries an additional phosphate group. NADP+ and NADPH often serve in biosynthetic and antioxidant reactions, while NAD+ and NADH are more associated with energy-yielding catabolism. Nicotinamide, nicotinic acid, and nicotinamide riboside are precursors that can enter salvage pathways. The exact contribution of dietary precursors to tissue NAD+ pools is an area of active investigation. Some studies measure labeled precursors to trace those routes.
NAD+ is the oxidized form of nicotinamide adenine dinucleotide, a coenzyme built from two nucleotides joined by a phosphate linkage. One nucleotide carries adenine, and the other carries nicotinamide; the plus sign denotes a formal positive charge on the nicotinamide ring, not a free proton. In cells, NAD+ and its reduced partner NADH form a reversible redox pair. That pair participates in electron transfer reactions throughout metabolism. The abbreviation NAD+ is common in biochemistry, while NAD(H) sometimes denotes the combined pool.
It contains a syringe-like reservoir with about three days' insulin supply. This is connected by thin, disposable, plastic tubing to a needle-like cannula inserted into the patient's skin and held in place by an adhesive patch. The infusion tubing and cannula must be removed and replaced every few days. An insulin pump can be programmed to infuse a steady amount of rapid-acting insulin under the skin. This steady infusion is termed the basal rate and is designed to supply the background insulin needs. Each time the patient eats, he or she must press a button on the pump to deliver a specified dose of insulin to cover that meal. Extra insulin is also given the same way to correct a high glucose reading. Although current pumps can include a glucose sensor, they cannot automatically respond to meals or to rising or falling glucose levels. Both MDI and pumping can achieve similarly excellent glycemic control. Some people prefer injections because they are less expensive than pumps and do not require the wearing of a continually attached device. However, the clinical literature is very clear that patients whose basal insulin requirements tend not to vary throughout the day or do not require dosage precision smaller than 0.5 IU, are much less likely to realize much significant advantage of pump therapy. Another perceived advantage of pumps is the freedom from syringes and injections, however, infusion sets still require less frequent injections to guide infusion sets into the subcutaneous tissue. Intensive/flexible insulin therapy requires frequent blood glucose checking.
== A == AACTG – acquired immunity – acquired immunodeficiency syndrome (AIDS) – ACT UP/Golden Gate – active immunity – acupuncture – acute HIV infection – Acute HIV Infection and Early Diseases Research Program (AIEDRP) – ADAP – ADC – adenopathy – adherence – adjuvant – administration – Adult AIDS Clinical Trials Group (AACTG) – adverse drug reaction – aerosolized – AETC – agammaglobulinemia – Agency for Healthcare Research and Quality (AHRQ) – AHRQ – AIDS – AIDS Arms – AIDS dementia complex (ADC) – AIDS Drug Assistance Programs (ADAP) – AIDS education and training centers (AETC) – AIDS orphan – AIDS research advisory committee (ARAC) – AIDS service organization (ASO) – The AIDS Show – AIDS Vaccine 200 – AIDS Vaccine Advocacy Coalition – AIDS wasting syndrome – AIDS-related cancer – AIDS-related complex (ARC) – alkaline phosphatase – alopecia – alpha interferon (INFa) – alternative medicine – alveolar – amebiasis – amino acids – anaphylactic shock – anemia – anergy – angiogenesis – angiomatosis – anorexia – antenatal – antibiotic – antibodies – antibody-dependent cell-mediated cytotoxicity (ADCC) – antibody-mediated immunity – antifungal medication – antigen – antigen presentation – antigen-presenting cell (APC) – antineoplastic – antiprotozoal – antiretroviral drugs – antisense drugs – antitoxins – Antiviral drug – aphasia – aphthous ulcer – apoptosis – approved drugs – ARC – Armenicum – ART – arthralgia – ASO – aspergillosis – assembly and budding – asymptomatic – ataxia – attenuated – autoantibody – autoimmunization – autoinoculation – autologous – avascular necrosis (AVN) – AVN
Minoxidil was discovered in 1963 and was introduced for treatment of high blood pressure in 1971. In 1971, researchers unexpectedly discovered that minoxidil causes hair growth, resulting in it being repurposed for treatment of hair loss and approved in topical form for this use in 1988. Topical minoxidil became available over-the-counter in 1996. Low-dose oral minoxidil (LDOM) emerged for treatment of hair loss in 2015 and dramatically increased in popularity starting in 2022. Extended-release oral minoxidil and sublingual minoxidil were developed in the 2020s for hair loss and are in late-stage trials. Aside from its use in humans, minoxidil is extremely toxic to cats and dogs even in small amounts.
=== Finnish === Examples of long words that have been in everyday use in the Finnish language are kolmivaihekilowattituntimittari which means "three-phase kilowatt hour meter" (31 letters), liikekannallepanotarkastuskierros ("mobilization inspection round", 33 letters), peruspalveluliikelaitoskuntayhtymä ("a public utility of a municipal federation for provision of basic services", 34 letters), and lentokonesuihkuturbiinimoottoriapumekaanikkoaliupseerioppilas "airplane jet turbine engine auxiliary mechanic non-commissioned officer student" (61 letters), an actual military term, although one which has been deprecated. The longest military term in current use is vastatykistömaalinosoitustutkakalustojärjestelmäinsinöörierikoisupseeri "counter-artillery targeting radar systems engineer specialist officer" with 71 characters, with 2 more if grammatically incorrect extra hyphens added for readability are counted. If conjugated forms are allowed, even longer real words can be made. Allowing derivatives and clitics allows the already lengthy word to grow even longer, although the usability of the word starts to degrade. Because Finnish uses free forming of composite words, new words can even be formed during a conversation. One can add nouns after each other without breaking grammar rules. If one allows artificial constructs as well as using clitics and conjugated forms, one can create even longer words: such as kumarreksituteskenteleentuvaisehkollaismaisekkuudellisennesk- enteluttelemattomammuuksissansakaankopahan (102 letters), which was created by Artturi Kannisto.
Sources: en.wikipedia.org
Increasingly restrictive drug laws of the 1960s and the 1970s curbed scientific research into the effects of psilocybin and other hallucinogens, but its popularity as an entheogen grew in the next decade, owing largely to the increased availability of information on how to cultivate psilocybin mushrooms. Possession of psilocybin-containing mushrooms has been outlawed in most countries, and psilocybin is classified as a Schedule I controlled substance in the 1971 United Nations Convention on Psychotropic Substances. Psilocybin is being studied as a possible medicine in the treatment of psychiatric disorders such as major depressive disorder, substance use disorders, obsessive–compulsive disorder, and other conditions such as cluster headaches. Psilocybin was approved for treatment-resistant depression in Australia in 2023. It is in late-stage clinical trials in the United States for major depressive disorder and treatment-resistant depression. As of September 2026, complete submission of psilocybin for treatment-resistant depression is expected in the fourth quarter of 2026 and commercial launch for this indication is anticipated in the first half of 2027. Especially at higher doses and combined with psychological support, single doses of psilocybin may produce rapid and long-lasting antidepressant effects that outperform placebo, though they may produce either modest or no effectiveness advantage over continuous use of selective serotonin reuptake inhibitors (SSRIs) like escitalopram and trial methodological issues are common.
=== Inhalation === Airborne MNPs originate from urban dust, rubber tires, household plastic items, and synthetic fibers from textiles. It is also theorized that particles that have entered our waterways can become suspended in the air via wave action, as well as via the spreading of wastewater treatment sludge on agricultural fields. Once inhaled, these particles may become lodged in the lungs or, through mucociliary clearance, be ingested and enter the digestive system. Airborne microplastics have been detected in urban atmospheres, with reports showing a fallout of 29–280 particles per square meter per day on an urban rooftop, underscoring the potential for routine exposure. Annual inhalation exposure rates vary, with some studies estimating individuals inhale up to 68,000 particles each year. Children are at higher risk of exposure to MNPs by inhalation. When compared to adults, children have less efficient nasal filtering, are more typically mouth breathers, and breathe more air per unit of body mass. This makes them more susceptible to air pollutants of all kinds.
MHC Class II molecules are a class of major histocompatibility complex (MHC) molecules normally found only on professional antigen-presenting cells such as dendritic cells, macrophages, some endothelial cells, thymic epithelial cells, and B cells. These cells are important in initiating immune responses. Antigens presented by MHC class II molecules are exogenous, originating from extracellular proteins rather than cytosolic and endogenous sources like those presented by MHC class I. The loading of a MHC class II molecule occurs by phagocytosis. Extracellular proteins are endocytosed into a phagosome, which subsequently fuses with a lysosome to create a phagolysosome. Within the phagolysosome, lysosomal enzymes degrade the proteins into peptide fragments. These fragments are then loaded into the peptide-binding groove of the MHC class II molecule. Once loaded, the MHC class II-peptide complexes are transported to the plasma membrane via vesicular transport, where they present the antigens to the extracellular environment. In humans, the MHC class II protein complex is encoded by the human leukocyte antigen gene complex (HLA). Class II HLAs are composed of the classical HLA-DP, HLA-DQ, and HLA-DR and non-classical HLA-DM and HLA-DO MHC molecules.
== Deficiency == Plasma vitamin C is the most widely applied test for vitamin C status. Adequate levels are defined as near 50 μmol/L. Hypovitaminosis of vitamin C is defined as less than 23 μmol/L, and deficiency as less than 11.4 μmol/L. For people 20 years of age or above, data from the US 2017–18 National Health and Nutrition Examination Survey showed mean serum concentrations of 53.4 μmol/L. Deficiency was reported in 5.9% of people. Globally, vitamin C deficiency is common in low and middle-income countries, and not uncommon in high income countries. In the latter, prevalence is higher in males than in females. Plasma levels are considered saturated at about 65 μmol/L, achieved by intakes of 100 to 200 mg/day, which are well above the recommended intakes. Even higher oral intake does not further raise plasma nor tissue concentrations because absorption efficiency decreases and any excess that is absorbed is excreted in urine.
== Medical uses == Doxepin is used as a pill to treat major depressive disorder, anxiety disorders, and chronic hives, and for short-term help with trouble remaining asleep after going to bed (a form of insomnia). As a cream it is used for short-term treatment of itchiness caused by atopic dermatitis or lichen simplex chronicus.
Sources: en.wikipedia.org
==== Energy and climate ==== The Duterte administration initially adopted a "technology neutral" policy in energy generation. Earlier in his term, Duterte stressed that coal remains the most viable source of energy if the Philippines is to accelerate industrialization, and questioned the sanctions imposed by the United States and European Union on smaller countries including the Philippines when the country's carbon footprint is not significant compared to the superpowers. The administration shifted its energy policy to prefer renewable sources of energy later in Duterte's term. At his fourth State of the Nation address in July 2019, Duterte issued an order to cut coal dependence and hasten a transition to renewable energy. In October 2020, the energy department issued a moratorium on the construction of new coal power plants and favored renewable energy sources. On February 28, 2022, Duterte issued an executive order approving the inclusion of nuclear power in the country's energy mix. To hasten the expansion of the nation's power capacity, Duterte established the inter-agency Energy Investment Coordinating Council tasked with simplifying and streamlining the approval process of big-ticket projects. On January 21, 2022, he signed a law promoting the use of microgrid systems in unserved and underserved areas to accelerate total electrification of the country. The administration made initiatives to liberalize the energy sector, allowing 100% foreign ownership in large-scale geothermal projects starting October 2020.
From the early days of the development of AI, there have been arguments put forward by ELIZA creator Joseph Weizenbaum and others about whether tasks that can be done by computers actually should be done by them, given the difference between computers and humans, and between quantitative calculations and qualitative, value-based judgements. In April 2023, it was reported that image generation AI has resulted in 70% of the jobs for video game illustrators in China being lost. In July 2023, developments in generative AI contributed to the 2023 Hollywood labor disputes. Fran Drescher, president of the Screen Actors Guild, declared that "artificial intelligence poses an existential threat to creative professions" during the 2023 SAG-AFTRA strike. Voice generation AI has been seen as a potential challenge to the voice acting sector. However, a 2025 study concluded that the US labor market had so far not experienced a discernible disruption from generative AI. Another study reported that Danish workers who used chatbots saved 2.8% of their time on average, and found no significant change in earnings or hours worked.
=== In vivo === Phosphatidylcholine is a major phospholipid in eukaryotic cell membranes. Close regulation of its biosynthesis, degradation, and distribution is essential to proper cell function. Phosphatidylcholine is synthesized in vivo by two pathways
=== Patient information === Blood Transfusion Leaflets (NHS Blood and Transplant) Blood Transfusion Leaflets (Welsh Blood Service) Blood Transfusion Information (Scotland) Blood Transfusion Information (Australia) Blood Transfusion Information (American Cancer Society)
Sources: en.wikipedia.org
NAD+ is a coenzyme found in living cells and is the oxidized form of nicotinamide adenine dinucleotide. It accepts electrons in redox reactions and also serves as a substrate for certain signaling and repair enzymes.
NAD+ becomes NADH when it accepts a hydride ion during oxidation-reduction reactions. NADH then donates electrons to other molecules, after which the carrier can return to the NAD+ form.
No, nicotinamide is a smaller molecule and a component of NAD+. Cells can use nicotinamide to rebuild NAD+ through the salvage pathway.
NAD+ is a coenzyme found in all living cells. It carries electrons in metabolic reactions and also serves as a substrate for enzymes involved in signaling and DNA repair. Its oxidized and reduced forms are central to energy metabolism.