Niacin

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WHAT IS NIACIN?

Niacin , also known as vitamin B3, nicotinamide, and nicotinic acid, is an important part of the B-complex. Without it, the body cannot metabolize carbohydrates, fats, and proteins to provide energy. It also helps keep the health and vitality of the skin, digestive tract, and nerves.

Niacin (vitamin B3) is unique among the B vitamins because it can be manufactured by the body. About half of the niacin our bodies use comes from food. Our bodies make the other half from the amino acid tryptophan. When tryptophan is consumed, our bodies first use it to build needed body proteins. Leftover tryptophan is used to make niacin.

Niacin is a water-soluble vitamin, more commonly known as nicotinamide.

It and plays an important role in the biosynthesis of purine nucleotides. This nitrogen heterocyclic biochemical is combined in vivo with the nucleotide adenosine to form to niacinamide, which is a constituent of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are coenzymes involved in glycogenolysis , tissue respiration and lipid metabolism. NAD functions as an electron carrier for intracellular respiration , as well as a codehydrogenase with enzymes involved in the oxidation of fuel molecules. Nicotinamide adenine dinucleotide, NADH, plays a central role in oxidative metabolism . Through the mitochondrial electron transport chain, NADH can transfer two electrons and a hydrogen ion to oxygen, liberating 52.6 kcal/mole. This is enough energy to synthesize 7.2 ATPs from ADP and Pi. Some inefficiency, though, allows only 3 ATPs to be formed.

NADP functions as a hydrogen donor in reductive biosyntheses such as in fatty acid and steroid syntheses and, like NAD, as a codehydrogenase.

Since almost every cellular metabolic pathway uses a form of niacin, a diet deficient in niacin (as well as tryptophan) leads to glossitis of the tongue, dermatitis, weight loss, diarrhea, depression and dementia. The entire group of symptoms is associated with a disease known as pellagra . Several physiological conditions (e.g. Hartnup disease and malignant carcinoid syndrome) as well as certain drug therapies (e.g. isoniazid) can lead to niacin deficiency. In Hartnup disease tryptophan absorption is impaired and in malignant carcinoid syndrome tryptophan metabolism is altered resulting in excess serotonin synthesis. Isoniazid (the hydrazide derivative of isonicotinic acid) is the primary drug for chemotherapy of tuberculosis. Prolonged niacin deficiency often results in death.

 Niacin (nicotinic acid) has long been prescribed for the treatment of various cardiovascular conditions. It has been reported to be effective in lowering very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) while raising high-density lipoprotein (HDL) in serum. This has led to a lowering of plasma cholesterol by 10 to 15% and triglycerides by 20 to 30%, making it an useful therapeutic for hypercholesterolemia. The major action of nicotinic acid in this capacity is a reduction in fatty acid mobilization from adipose tissue. Although nicotinic acid therapy lowers blood cholesterol it also causes a depletion of glycogen stores and fat reserves in skeletal and cardiac muscle. The side effects of niacin, which may occur at the high dosages often required for therapeutic usage, have caused researchers to investigate niacin supplementation using niacin esters, particularly inositol hexaniacinate (IHN).

Nicotinamide is also under investigation for helping prevent and control diabetes. Nicotinamide protects beta cells from damage by oxygen radicals and nitric oxide. It also improves beta cell regeneration.

The most common side effect of niacin therapy is known as the "niacin flush." In large doses, niacin produces peripheral vasodilatation, a process believed to be mediated by prostacyclin, which affects the cutaneous vessels of the upper body. This causes a tingling effect that, if intense, can be very painful.

Niacin

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