Niacin
IUPAC name pyridine-3-carboxylic acid[1]
Systematic name Pyridine-3-carboxylic acid[2]
Other names Bionic Vitamin B3
Identifiers
CAS number	59-67-6 Y
PubChem	938
ChemSpider	913 Y
UNII	2679MF687A Y
EC number	200-441-0
DrugBank	DB00627
KEGG	D00049 Y
MeSH	Niacin
ChEBI	CHEBI:15940 Y
ChEMBL	CHEMBL573 Y
IUPHAR ligand	1588
RTECS number	QT0525000
ATC code	C04AC01,C10AD02
Beilstein Reference	109591
Gmelin Reference	3340
3DMet	B00073
Jmol-3D images	Image 1 Image 2
SMILES Oc(:o):c1cccnc1 OC(=O)C1=CN=CC=C1
InChI InChI=1S/C6H5NO2/c8-6(9)5-2-1-3-7-4-5/h1-4H,(H,8,9) Y Key: PVNIIMVLHYAWGP-UHFFFAOYSA-N Y InChI=1/C6H5NO2/c8-6(9)5-2-1-3-7-4-5/h1-4H,(H,8,9) Key: PVNIIMVLHYAWGP-UHFFFAOYAA
Properties
Molecular formula	C6NH5O2
Molar mass	123.1094 g mol-1
Appearance	White, translucent crystals
Density	1.473 g cm-3
Melting point	237 °C, 510 K, 458 °F
Solubility in water	18 g L-1
log P	0.219
Acidity (pKa)	2.201
Basicity (pKb)	11.796
Isoelectric point	4.75
Refractive index (nD)	1.4936
Dipole moment	0.1271305813 D
Thermochemistry
Std enthalpy of formation ΔfHo298	-344.9 kJ mol-1
Std enthalpy of combustion ΔcHo298	-2.73083 MJ mol-1
Pharmacology
Routes of administration	Intramuscular, Oral
Elimination half-life	20-45 min
Hazards
EU classification	Xi
R-phrases	R36/37/38
S-phrases	S26, S36
NFPA 704	1 1 0
Flash point	193 °C
Autoignition temperature	365 °C
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

"Niacin" redirects here. For the neo-fusion band, see Niacin (band).

Niacin (also known as vitamin B₃, nicotinic acid and vitamin PP) is an organic compound with the formula C₆H₅NO₂ and, depending on the definition used, one of the forty to eighty essential human nutrients.

Niacin is one of five vitamins (when lacking in human diet) associated with a pandemic deficiency disease: niacin deficiency (pellagra), vitamin C deficiency (scurvy), thiamin deficiency (beriberi), vitamin D deficiency (rickets), vitamin A deficiency (night blindness and other symptoms). Niacin has been used for over 50 years to increase levels of HDL in the blood and has been found to modestly decrease the risk of cardiovascular events in a number of controlled human trials.

This colorless, water-soluble solid is a derivative of pyridine, with a carboxyl group (COOH) at the 3-position. Other forms of vitamin B₃ include the corresponding amide, nicotinamide ("niacinamide"), where the carboxyl group has been replaced by a carboxamide group (CONH₂), as well as more complex amides and a variety of esters. Niacin and Vitamin B3 are the generic terms for both nicotinic acid and nicotinamide, which are often used interchangeably to refer to any member of this family of compounds, since they have similar biochemical activity.^[3]

Niacin cannot be directly converted to nicotinamide, but both compounds could be converted to NAD and NADP in vivo. Although the two are identical in their vitamin activity, nicotinamide does not have the same pharmacological effects (lipid modifying effects) as niacin. Nicotinamide does not reduce cholesterol or cause flushing.^[4] Nicotinamide may be toxic to the liver at doses exceeding 3 g/day for adults.^[5] Niacin is a precursor to NAD+/NADH and NADP+/NADPH, which play essential metabolic roles in living cells.^[6] Niacin is involved in both DNA repair, and the production of steroid hormones in the adrenal gland.

Dietary needs[link]

One recommended daily allowance of niacin is 2–12 mg/day for children, 14 mg/day for women, 16 mg/day for men, and 18 mg/day for pregnant or breast-feeding women.^[7] The upper limit for adult men and women is 35 mg/day, which is based on flushing as the critical adverse effect.^{[citation needed]} In general, niacin status is tested through urinary biomarkers,^[8] which are believed to be more reliable than plasma levels.^[9]

Deficiency[link]

At present, niacin deficiency is sometimes seen in developed countries, and it is usually apparent in conditions of poverty, malnutrition, and chronic alcoholism.^[10] It also tends to occur in areas where people eat maize (corn, the only grain low in digestible niacin) as a staple food. A special cooking technique called nixtamalization is needed to increase the bioavailability of niacin during maize meal/flour production.

Mild niacin deficiency has been shown to slow metabolism, causing decreased tolerance to cold.

Severe deficiency of niacin in the diet causes the disease pellagra, which is characterized by diarrhea, dermatitis, and dementia, as well as “necklace” lesions on the lower neck, hyperpigmentation, thickening of the skin, inflammation of the mouth and tongue, digestive disturbances, amnesia, delirium, and eventually death, if left untreated.^[11] Common psychiatric symptoms of niacin deficiency include irritability, poor concentration, anxiety, fatigue, restlessness, apathy, and depression.^[11] Studies have indicated that, in patients with alcoholic pellagra, niacin deficiency may be an important factor influencing both the onset and severity of this condition. Alcoholic patients typically experience increased intestinal permeability, leading to negative health outcomes.

Hartnup’s disease is a hereditary nutritional disorder resulting in niacin deficiency.^[11] This condition was first identified in the 1950s by the Hartnup family in London. It is due to a deficit in the intestines and kidneys, making it difficult for the body to break down and absorb dietary tryptophan. The resulting condition is similar to pellagra, including symptoms of red, scaly rash, and sensitivity to sunlight. Oral niacin is given as a treatment for this condition in doses ranging from 40–200 mg, with a good prognosis if identified and treated early.^[11] Niacin synthesis is also deficient in carcinoid syndrome, because of metabolic diversion of its precursor tryptophan to form serotonin.

Lipid-modifying effects[link]

Niacin binds to and stimulates a G-protein-coupled receptor, GPR109A, which causes the inhibition of fat breakdown in adipose tissue.^[12] Nicotinamide does not bind this receptor which explains why it does not affect blood lipid levels. Lipids that are liberated from adipose tissue are normally used to build very-low-density lipoproteins (VLDL) in the liver, which are precursors of low-density lipoprotein (LDL) or "bad" cholesterol. Because niacin blocks the breakdown of fats, it causes a decrease in free fatty acids in the blood and, as a consequence, decreases the secretion of VLDL and cholesterol by the liver.^[13]

By lowering VLDL levels, niacin also increases the level of high-density lipoprotein (HDL) or "good" cholesterol in blood, and therefore it is sometimes prescribed for people with low HDL, who are also at high risk of a heart attack.^[14][15]

The ARBITER 6-HALTS study, reported at the 2009 annual meeting of the American Heart Association and in the New England Journal of Medicine^[16] concluded that, when added to statins, 2000 mg/day of slow-release niacin was more effective than ezetimibe (Zetia) in reducing carotid intima-media thickness, a marker of atherosclerosis.^[17] Additionally, a recent meta-analysis covering 11 randomized controlled clinical trials found positive effects of niacin alone or in combination on all cardiovascular events and on atherosclerosis evolution.^[18]

However, a 2011 study (AIM-HIGH) was halted early because patients showed no decrease in cardiovascular events, but did experience an increase in the risk of stroke. These patients already had LDL levels well-controlled by a statin drug, and the aim of the study was to evaluate slow-release niacin (2000 mg per day) to see if raising HDL levels had an additional positive effect on risk. In this study, it did not have such an effect, and appeared to increase stroke risk.^[19] The role of niacin in patients whose LDL is not well-controlled (as in the majority of previous studies with niacin) is still under study and debate. However, it does not seem to offer benefits via raising HDL, in patients already lowering LDL by taking a statin.

Toxicity[link]

A man with pellagra, which is caused by a chronic lack of vitamin B₃ in the diet

Pharmacological doses of niacin (1.5 - 6 g per day) occasionally lead to side effects that can include dermatological conditions such as skin flushing and itching, dry skin, and skin rashes including eczema exacerbation and acanthosis nigricans. Some of these symptoms are generally related to niacin's role as the rate limiting cofactor in the histidine decarboxylase enzyme which converts l-histidine into histamine.^{[citation needed]} H1 and H2 receptor mediated histamine is metabolized via a sequence of mono (or di-) amine oxidase and COMT into methylhistamine which is then conjugated through the liver's CYP450 pathways. Persistent flushing and other symptoms may indicate deficiencies in one or more of the cofactors responsible for this enzymatic cascade. Gastrointestinal complaints, such as dyspepsia (indigestion), nausea and liver toxicity fulminant hepatic failure, have also been reported. Side effects of hyperglycemia, cardiac arrhythmias and "birth defects in experimental animals" have also been reported.^[20]

Flushing lasts for about 15 to 30 minutes, and is sometimes accompanied by a prickly or itching sensation, in particular, in areas covered by clothing. This effect is mediated by GPR109A-mediated prostaglandin release from the Langerhans cells of the skin and can be blocked by taking 300 mg of aspirin half an hour before taking niacin, by taking one tablet of ibuprofen per day or by co-administering the prostaglandin receptor antagonist laropiprant. Taking the niacin with meals also helps reduce this side effect. After several weeks of a consistent dose, most patients no longer flush.^[21] Slow- or "sustained"-release forms of niacin have been developed to lessen these side effects.^[13][22] One study showed the incidence of flushing was significantly lower with a sustained release formulation^[23] though doses above 2 g per day have been associated with liver damage, in particular, with slow-release formulations.^[20] Flushing is often thought to involve histamine, but histamine has been shown not to be involved in the reaction.^[24] Prostaglandin (PGD₂) is the primary cause of the flushing reaction, with serotonin appearing to have a secondary role in this reaction.^[24]

Although high doses of niacin may elevate blood sugar, thereby worsening diabetes mellitus,^[20] recent studies show the actual effect on blood sugar to be only 5–10%. Patients with diabetes who continued to take anti-diabetes drugs containing niacin did not experience major blood glucose changes. Thus looking at the big picture, niacin continues to be recommended as a drug for preventing cardiovascular disease in patients with diabetes.

Hyperuricemia is another side effect of taking high-dose niacin, and may exacerbate gout.^[25]

Niacin in doses used to lower cholesterol levels has been associated with birth defects in laboratory animals, with possible consequences for infant development in pregnant women.^[20]

Niacin, particularly the time-release variety, at extremely high doses can cause acute toxic reactions.^[26] Extremely high doses of niacin can also cause niacin maculopathy, a thickening of the macula and retina, which leads to blurred vision and blindness. This maculopathy is reversible after niacin intake ceases.^[27]

Nicotinamide[link]

Nicotinamide may be obtained from the diet where it is present primarily as NAD+ and NADP+. These are hydrolysed in the intestine and the resulting nicotinamide is absorbed either as such, or following its hydrolysis to nicotinic acid. nicotinamide are present in nature in only small amounts. In unprepared foods, niacin is present mainly in the form of the cellular pyridine nucleotides NAD and NADP. Enzymatic hydrolysis of the co-enzymes can occur during the course of food preparation. Boiling releases most of the total niacin present in sweet corn as nicotinamide (up to 55 mg/kg).^[3]

Inositol hexanicotinate[link]

One form of dietary supplement is inositol hexanicotinate (IHN), which is inositol that has been esterified with niacin on all six of inositol's alcohol groups. IHN is usually sold as "flush-free" or "no-flush" niacin in units of 250, 500, or 1000 mg/tablets or capsules. It is sold as an over-the-counter formulation, and often is marketed and labeled as niacin, thus misleading consumers into thinking they are getting the active form of the medication. While this form of niacin does not cause the flushing associated with the immediate-release products, the evidence that it has lipid-modifying functions is contradictory, at best. As the clinical trials date from the early 1960s (Dorner, Welsh) or the late 1970s (Ziliotto, Kruse, Agusti), it is difficult to assess them by today's standards.^[28] One of the last of those studies affirmed the superiority of inositol and xantinol esters of nicotinic acid for reducing serum free fatty acid,^[29] but other studies conducted during the same period found no benefit.^[30] Studies explain that this is primarily because "flush-free" preparations do not contain any free nicotinic acid. A more recent placebo-controlled trial was small (n=11/group), but results after three months at 1500 mg/day showed no trend for improvements in total cholesterol, LDL-C, HDL-C or triglycerides.^[31] Thus, so far there is not enough evidence to recommend IHN to treat dyslipidemia. Furthermore, the American Heart Association and the National Cholesterol Education Program both take the position that only prescription niacin should be used to treat dyslipidemias, and only under the management of a physician. The reason given is that niacin at effective intakes of 1500–3000 mg/day can also potentially have severe adverse effects. Thus liver function tests to monitor liver enzymes are necessary when taking therapeutic doses of niacin, including alkaline phosphatase (ALP), aspartate transaminase (AST), and alanine transaminase (ALT).

Biosynthesis and chemical synthesis[link]

Biosynthesis

The liver can synthesize niacin from the essential amino acid tryptophan, requiring 60 mg of tryptophan to make one mg of niacin.^[7] The 5-membered aromatic heterocycle of tryptophan is cleaved and rearranged with the alpha amino group of tryptophan into the 6-membered aromatic heterocycle of niacin. Riboflavin, vitamin B₆ and iron are required in some of the reactions involved in the conversion of tryptophan to NAD.

Several million kilograms of niacin are manufactured each year, starting from 3-methylpyridine.

Receptor[link]

In addition to its effects as NAD and NADP, niacin may have additional effects by receptor activation. The receptor for niacin is a G protein-coupled receptor called HM74A.^[32] It couples to the Gi alpha subunit.^[33]

Food sources[link]

Niacin is found in variety of foods, including liver, chicken, beef, fish, cereal, peanuts and legumes, and is also synthesized from tryptophan, which is found in meat, dairy and eggs.

Animal products:

• liver, heart and kidney
• whalemeat Meke Whale
• chicken, chicken breast
• beef
• fish: tuna, salmon, halibut
• eggs

Fruits and vegetables:

• avocados
• dates
• tomatoes
• leaf vegetables
• broccoli
• carrots
• sweet potatoes
• asparagus

Seeds:

• nuts
• whole grain products
• legumes
• saltbush seeds

Fungi:

• mushrooms, shiitake mushrooms
• brewer's yeast

Other:

• Vegemite (from spent brewer's yeast)
• Tofu
• Soy Sauce

History[link]

Niacin was first described by Austrian chemist Hugo Weidel in 1873 in his studies of nicotine.^[34] The original preparation remains useful: The oxidation of nicotine using nitric acid.^[35] Niacin was extracted from livers by Norweigan biochemist Conrad Elvehjem, who later identified the active ingredient, then referred to as the "pellagra-preventing factor" and the "anti-blacktongue factor."^[36] When the biological significance of nicotinic acid was realized, it was thought appropriate to choose a name to dissociate it from nicotine, to avoid the perception that vitamins or niacin-rich food contains nicotine, or that cigarettes contain vitamins. The resulting name 'niacin' was derived from nicotinic acid + vitamin.

Carpenter found in 1951 that niacin in corn is biologically unavailable, and can be released only in very alkaline lime water of pH 11.^[37] This process, known as nixtamalization, was discovered by the prehistoric civilizations of Mesoamerica.^[38]

Niacin is referred to as vitamin B₃ because it was the third of the B vitamins to be discovered. It has historically been referred to as "vitamin PP" or "vitamin P-P".

Research[link]

As of August 2008^[update], a combination of niacin with laropiprant is being tested in a clinical trial. Laropiprant reduces facial flushes induced by niacin.^[39]

References[link]

External links[link]

• Niacin bound to proteins in the PDB

This article may contain original research. Please improve it by verifying the claims made and adding references. Statements consisting only of original research may be removed. More details may be available on the talk page. (February 2008)

Billy Sheehan
Background information
Birth name	William Sheehan
Born	(1953-03-19) March 19, 1953 (age 59) Buffalo, New York, USA
Genres	Hard rock, heavy metal, jazz fusion, instrumental rock, progressive rock
Occupations	Musician, songwriter
Instruments	Bass, guitar, vocals, harmonica,
Years active	1970–present
Associated acts	UFO, David Lee Roth, Mr. Big, Richie Kotzen, Marty Friedman, Tim "Ripper" Owens, Talas, B'z, Steve Vai, G3, Niacin
Website	Billy Sheehan on Myspace

William "Billy" Sheehan (born on March 19, 1953, in Buffalo, New York) is an American bassist known for his work with Talas, Steve Vai, David Lee Roth, Mr. Big, and Niacin. Sheehan has won the "Best Rock Bass Player" readers' poll from Guitar Player Magazine five times for his "lead bass" playing style.^[1] Sheehan's repertoire includes the use of chording, two-handed tapping, right-hand "three-finger picking" technique and controlled feedback.

Career[link]

Early years[link]

Billy Sheehan's first electric bass was a Hagström FB, which was soon sistered^{[clarification needed]} by a Precision bass similar to Tim Bogert's. After acquiring the Precision bass, he removed the frets from the Hagström. Over the years, he heavily modified the Precision bass as well, adding a neck pickup and additional support for the bolt-on neck, which Sheehan considers its greatest weakness. The neck pickup was added for what Sheehan referred to as "super deep low end" modelled after Paul Samwell-Smith of the Yardbirds. The Gibson EB-0 type pickup in the neck and the original split Precision bass pickup each have their own separate output jacks on the bass itself, allowing for control of the tone via the bass. Sheehan also uses two amps to achieve his signature tone (as do Chris Squire of Yes and Doug Pinnick of King's X), one with full distortion and notch filtering to sound more guitar-like for solos, and one super-clean for the low end of the neck pickup. This bass has been retired, but he affectionately refers to it as "The Wife"."Gear article". Billysheehan.com. http://billysheehan.com/gear/instruments_34.html. Retrieved 2011-08-09.  Sheehan's signature Yamaha bass is based on this Bass.

Sheehan's first full-time band was Talas, a power trio with Dave Constantino on guitar and Paul Varga on drums. The band played a mixture of cover songs and original material, and all three instrumentalists alternated on lead vocals.

Talas was one of Buffalo's most popular local bands for over a decade, arguably attaining cult status which spread into the northeast US and into Canada. In 1978, Talas released their eponymous debut album, which generated the regional hit single, "See Saw". It was during this time that Sheehan wrote some of his most famous songs, namely "Shy Boy" (later re-recorded with David Lee Roth), and the complex and frenetic "Addicted to that Rush" (later re-recorded with Mr Big).

In the late 1970s, Sheehan also played in a band called Light Years with drummer Ron Rocco who had earlier played in a band called Black Sheep with Foreigner singer Lou Gramm in Rochester, NY. After Sheehan returned to Talas they opened a show for UFO in Buffalo. This led Sheehan to an association with guitarist Michael Schenker and also helped land him the job touring with UFO in 1983.

Talas' first national exposure happened in 1980, when they opened thirty shows for Van Halen. However, success was elusive, and even as their brand of what came to be known as "glam metal" gained popularity over the next few years, Talas remained an unsigned act, due largely to poor management. They independently released their debut eponymous "Talas" LP on Evenfall Records (reissued by Metal Blade) and then "Sink Your Teeth Into That" on Relativity Records.

Seeking to take Talas further than just regional success, Sheehan reformed Talas with another drummer (Mark Miller), guitarist (Mitch Perry, also later of Heaven), and a dedicated vocalist, Phil Naro, with whom in the late 1970s Sheehan had previously worked in his side project (the Billy Sheehan Band). Talas would release only one more album, Live Speed on Ice. After Mitch Perry left the band, he was replaced by Johnny Angel, who played guitar with them for their 1985/86 US tour opening for Yngwie Malmsteen's Rising Force. There was a fourth Talas record, tentatively titled "Lights, Camera, Action" to be issued on Gold Mountain/A&M, but it never got past the demo stage due to Sheehan leaving to join David Lee Roth's solo band. Talas did briefly continue on under Phil Naro sans Sheehan, enlisting Jimmy Degrasso on drums, Al Pitrelli on guitar and Bruno Ravel on bass, but by this time Talas was dead Ravel joining Danger Danger.

In the early 1980s, Sheehan became involved with the proto-thrash metal band Thrasher, during this time he shared the stage with future Anthrax guitarist Dan Spitz. His involvement with Thrasher did not last long but he did play on 2 songs from the self titled LP, which has not been released on cd to date.

2000-present[link]

In January 2009 Billy Sheehan reunited with his old Mr Big band members: Eric Martin, Paul Gilbert and Pat Torpey for a reunion tour in Japan. In April 2009 Sheehan's third solo album, Holy Cow!, produced by Simone Sello, was released by Mascot Records. The album features guest appearances from Paul Gilbert, ZZ Top's Billy Gibbons and King's X bassist Doug Pinnick. Gilbert has stated in an interview that his amicable collaboration with Billy on Holy Cow!, recorded prior to January, was likely a factor in the decision to reunite Mr Big.^[2] Mr. Big is still together and their new album What If... produced by Kevin Shirley^[3] was released December 15, 2010 in Japan, and January 21, 2011 in Europe. It was released February 8, 2011 in the U.S.

Personal life[link]

Sheehan has been an active member of the Church of Scientology since 1971^[4] and appeared on the street offering to defend it during Project Chanology.^[5]

Partial discography[link]

With Talas[link]

• 1979: Talas
• 1982: Sink Your Teeth Into That
• 1983: High Speed On Ice
• 1990: Talas Years
• 1998: If We Only Knew Then What We Know Now
• 1998: Live In Buffalo

With Thrasher[link]

• 1985: Burning at the Speed of Light

Tony MacAlpine[link]

• 1986: Edge of Insanity

David Lee Roth[link]

• 1986: Eat 'Em and Smile
• 1988: Skyscraper

Mr. Big[link]

• 1989: Mr. Big
• 1991: Lean Into It
• 1993: Bump Ahead
• 1996: Hey Man
• 2000: Get Over It
• 2001: Actual Size
• 2011: What If...

Niacin[link]

• 1996: Niacin
• 1997: Live
• 1998: High Bias
• 2000: Live! Blood, Sweat & Beers
• 2000: Deep
• 2001: Time Crunch
• 2005: Organik

With Explorer's Club[link]

• 1998: Age of Impact

Solo[link]

• 2001: Compression
• 2005: Cosmic Troubadour'
• 2006: Prime Cuts
• 2009: Holy Cow

Terry Bozzio and Billy Sheehan[link]

• 2002: Nine Short Films

See also[link]

• Bx3
• Mr. Big
• Bass Frontiers Magazine

References[link]

External links[link]

Wikimedia Commons has media related to: Billy Sheehan

• Official website
• Billy's solo with Mr Big
• HardRadio.com interview by Joey Vera with Billy Sheehan Part 1
• HardRadio.com interview by Joey Vera with Billy Sheehan Part 2
• Interview with Billy Sheehan..., 8/01/2009
• Extensive CD collection published by or with participation of Billy Sheehan - continuously updated