Nervous system niacin

A deficiency of niacin also affects the nervous system. Numbness is initially observed and later, paralysis, particularly in the extremities is common. Severe cases are characteri2ed by tremor and a spastic or ataxic gait and are frequentiy associated with peripheral neuritis. Left untreated, severe thought disorders can ensue (1). 

Vitamin B6-coenzyme is involved in a variety of reactions, e.g., in the immune system, gluconeogenesis, erythrocyte fimction, niacin formation, nervous system, lipid metabolism, and in hormone modulation/gene expression [1, 2]. 

Vitamin B6 occurs naturally in three related forms pyridoxine (6.26 the alcohol form), pyridoxal (6.27 aldehyde) and pyridoxamine (6.28 amine). All are structurally related to pyridine. The active co-enzyme form of this vitamin is pyridoxal phosphate (PLP 6.29), which is a co-factor for transaminases which catalyse the transfer of amino groups (6.29). PLP is also important for amino acid decarboxylases and functions in the metabolism of glycogen and the synthesis of sphingolipids in the nervous system. In addition, PLP is involved in the formation of niacin from tryptophan (section 6.3.3) and in the initial synthesis of haem. 

Coenzymes The pyruvate dehydrogenase complex contains five coenzymes that act as carriers or oxidants for the intermediates of the reactions shown in Figure 9.3. Ei requires thiamine pyrophosphate, Ep requires lipoic acid and coenzyme A, and E3 requires FAD and NAD+. [Note Deficiencies of thiamine or niacin can cause serious central nervous system problems. This is because brain cells are unable to produce sufficient ATP (via the TCA cycle) for proper function if pyruvate dehydrogenase is inactive.]... 

Hartnup disease is a rare genetic condition in which there is a defect of the membrane transport mechanism for tryptophan and other large neutral amino acids. The result is that the intestinal absorption of free tryptophan is impaired, although dipeptide absorption is normal. There is a considerable urinary loss of tryptophan (and other amino acids) as a result of the failure of the normal reabsorption mechanism in the renal tubules - renal aminoaciduria. In addition to neurological signs that can be attributed to a deficit of tryptophan for the synthesis of serotonin in the central nervous system, the patients show clinical signs of pellagra, which respond to the administration of niacin. 

Deficiency in niacin causes pellagra (rough skin). Pellagra involves the skin and digestive cmd nervous system. Symptoms are the 4 D s Dermatitis, Diarrhea, Dementia, Death. Niacin also has vasodilating activity. 

This chapter discusses the pathways by which L-tryptophan is metabolized into a variety of metabolites, many of which have important physiological functions. A few metabolites are cited here briefly. Quinolinic acid is involved in the regulation of gluconeogenesis. Picolinic acid is involved in normal intestinal absorption of zinc. The body s pool of nicotinamide adenine dinucleotide (NAD) is influenced by L-tryptophan s metabolic conversion to niacin. Finally, L-tryptophan is the precursor of several neuroactive compounds, the most important of which is serotonin (5-HT), which participates as a neurochemical substrate for a variety of normal behavioral and neuroendocrine functions. Serotonin derived from L-tryptophan allows it to become involved in behavioral effects, reflecting altered central nervous system function under conditions that alter tryptophan nutrition and metabolism. 

Niacin plays a number of essential roles in the body. It is necessary for cell respiration metabolism of proteins, fats, and carbohydrates the release of energy from foods the secretion of digestive enzymes the synthesis of sex hormones and the proper functioning of the nervous system. It is also involved in the production of serotonin, an essential... 

Niacin deficiency leads to unwanted multisystemic problems that are often associated with dermatological changes. Pellagra is a condition in which niacin deficiency causes a symmetrical pigmented rash, thickened skin and superficial scaling which are found in sun-exposed body areas. The classic triad of niacin deficiency are the three D s—dermatitis, diarrhoea and dementia (Hegyi et al. 2004). Some of the effects on the central nervous system include depression, anxiety, restlessness and poor concentration. In addition, alcoholic individuals with poor nutrition can develop pellagroid encephalopathy (Cook et al. 1998). The role of niadn deficiency in cardiovascular disease and lipid metabolism remains to be fully explored. 

The definition of a vitamin has been extended by some (Spector, 1980) to Include those chemical compounds required by a specific tissue but not synthesized by that tissue. For example. In certain species, vitamin C can be synthesized from glucose In the liver but not In the Central Nervous System therefore, vitamin C Is not considered a vitamin for these animals. Vitamin C for the brain must be drawn from the blood, from the vitamin C that entered the blood from the diet, or was synthesized In the liver. Subsequently, vitamin C could be considered a vitamin for the brain since It must be obtained from outside the brain. Another example Is the vitamin niacin, which cannot be synthesized from tryptophane In mammalian brain however, the synthesis of niacin from tryptophane occurs In mammalian liver (Spector and Kelly, 197.9 Spector, 1979). 

Spector, R., 1979, Niacin and niacinamide transport In the central nervous system, J. Neurochem., 33 1285. 

Niacin is vital for energy release in tissues and cells. Working with riboflavin and thiamin, it helps to maintain healthy nervous and digestive systems. It is essential for growth and is involved in the synthesis of hormones. 

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