Niacin Metabolism and Parkinson\rqs Disease

Epidemiological surveys suggest an important role for niacin in the causes of Parkinson’s disease, in that niacin deficiency, the nutritional condition that causes pellagra, appears to protect against Parkinson’s disease. Absorbed niacin is used in the synthesis of nicotinamide adenine dinucleotide (NAD) in the body, and in the metabolic process NAD releases nicotinamide by poly(ADP-ribosyl)ation, the activation of which has been reported to mediate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson’s disease. Recently nicotinamide N-methyltransferase (EC2.1.1.1) activity has been discovered in the human brain, and the released nicotinamide may be methylated to 1-methylnicotinamide (MNA), via this enzyme, in the brain. A deficiency in mitochondrial NADH:ubiquinone oxidoreductase (complex I) activity is believed to be a critical factor in the development of Parkinson’s disease. MNA has been found to destroy several subunits of cerebral complex I, leading to the suggestion that MNA is concerned in the pathogenesis of Parkinson’s disease. Based on these findings, it is hypothesized that niacin is a causal substance in the development of Parkinson’s disease through the following processes: NAD produced from niacin releases nicotinamide via poly(ADP-ribosyl)ation, activated by the hydroxyl radical. Released excess nicotinamide is methylated to MNA in the cytoplasm, and superoxides formed by MNA via complex I destroy complex I subunits directly, or indirectly via mitochondrial DNA damage. Hereditary or environmental factors may cause acceleration of this cycle, resulting in neuronal death.

Niacin metabolism and Parkinson's disease

Epidemiological surveys suggest an important role for niacin in the causes of Parkinson's disease, in that niacin deficiency, the nutritional condition that causes pellagra, appears to protect against Parkinson's disease. Absorbed niacin is used in the synthesis of nicotinamide adenine dinucleotide (NAD) in the body, and in the metabolic process NAD releases nicotinamide by poly(ADP-ribosyl)ation, the activation of which has been reported to mediate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease. Recently nicotinamide N-methyltransferase (EC2.1.1.1) activity has been discovered in the human brain, and the released nicotinamide may be methylated to 1-methylnicotinamide (MNA), via this enzyme, in the brain. A deficiency in mitochondrial NADH: ubiquinone oxidoreductase (complex 1) activity is believed to be a critical factor in the development of Parkinson's disease. MNA has been found to destroy several subunits of cerebral complex 1, leading to the suggestion that MNA is concerned in the pathogenesis of Parkinson's disease. Based on these findings, it is hypothesized that niacin is a causal substance in the development of Parkinson's disease through the following processes: NAD produced from niacin releases nicotinamide via poly(ADP-ribosyl)ation, activated by the hydroxyl radical. Released excess nicotinamide is methylated to MNA in the cytoplasm, and superoxides formed by MNA via complex I destroy complex 1 subunits directly, or indirectly via mitochondrial DNA damage. Hereditary or environmental factors may cause acceleration of this cycle, resulting in neuronal death.

EFFECTS OF NICOTINAMIDE SUPPLEMENT ON BEHAVIORS IN OPEN-FIELD TEST OF RESTRAINED RATS / 营养学报

Objective: To study the effects of different niacin nutritures on behaviors of stressed rats. Methods: 100 Wistar male rats were assigned into 10 groups:control, pair-fed, nicotinamide (NAM) deficiency (ND), low-dose NAM supplement (LNS 40 mg/kg diet) and high-dose NAM supplement (HNS 500 mg/kg diet), and the corresponding restrained groups. 24 h urinary excretion of N1-methylnicotinamide (NMN), body weight changes, behaviors in the open-field test, plasma cortisol, nitric oxide(NO) and liver nitric oxide synthase(NOS) were determined. Results: Compared with the control group, restrained rats had relatively lower urinary NMN. Both ND and restrainted stress retarded the body weight gains . Rats in the control and LNS groups had relatively shorter latency time in the open-field test. Restrained rats had higher plasma cortisol and NO than those in the corresponding control group. However, rats with HNS had the lowest plasma cortisol concentrations. Dietary supplement of NAM increased liver NOS . Conclusions: Restraint stress may increase niacin depletion and appropriate NAM supplement has positive effects on stress adaptation in rats.