Niacin in the long-term treatment of schizophrenia

Regulation of NAD+ metabolism in aging and disease

More than a century after discovering NAD⁺, information is still evolving on the role of this molecule in health and diseases. The biological functions of NAD⁺ and NAD⁺ precursors encompass pathways in cellular energetics, inflammation, metabolism, and cell survival. Several metabolic and neurological diseases exhibit reduced tissue NAD⁺ levels. Significantly reduced levels of NAD⁺ are also associated with aging, and enhancing NAD⁺ levels improved healthspan and lifespan in animal models. Recent studies suggest a causal link between senescence, age-associated reduction in tissue NAD⁺ and enzymatic degradation of NAD⁺. Furthermore, the discovery of transporters and receptors involved in NAD⁺ precursor (nicotinic acid, or niacin, nicotinamide, and nicotinamide riboside) metabolism allowed for a better understanding of their role in cellular homeostasis including signaling functions that are independent of their functions in redox reactions. We also review studies that demonstrate that the functional effect of niacin is partially due to the activation of its cell surface receptor, GPR109a. Based on the recent progress in understanding the mechanism and function of NAD⁺ and NAD⁺ precursors in cell metabolism, new strategies are evolving to exploit these molecules' pharmacological potential in the maintenance of metabolic balance.

Natural Medicines for Psychotic Disorders: A Systematic Review

Patients with psychotic disorders regularly use natural medicines, although it is unclear whether these are effective and safe. The aim of this study was to provide an overview of evidence for improved outcomes by natural medicines. A systematic literature search was performed through Medline, PsycINFO, CINAHL, and Cochrane until May 2015. In 110 randomized controlled trials, evidence was found for glycine, sarcosine, N-acetylcysteine, some Chinese and ayurvedic herbs, ginkgo biloba, estradiol, and vitamin B6 to improve psychotic symptoms when added to antipsychotics. Ginkgo biloba and vitamin B6 seemed to reduce tardive dyskinesia and akathisia. Results on other compounds were negative or inconclusive. All natural agents, except reserpine, were well tolerated. Most study samples were small, study periods were generally short, and most results need replication. However, there is some evidence for beneficial effects of certain natural medicines.

Niacin and vitamin B6 in mental functioning: a review of controlled trials in humans

Fifty-three controlled trials of the effects of niacin, vitamin B6, and multivitamins on mental functions are reviewed. The results are interpreted with emphasis on the methodological quality of the trials. It turns out that virtually all trials show serious short-comings: in the number of participants, the presentation of baseline characteristics and outcomes, and the description of changes in concomitant treatments. Only in autistic children are some positive results are found with very high dosages of vitamin B6 combined with magnesium, but further evidence is needed before more definitive conclusions can be drawn. For many other indications (hyperactive children, children with Down's syndrome, IQ changes in healthy schoolchildren, schizophrenia, psychological functions in healthy adults and geriatric patients) there is no adequate support from controlled trials in favor of vitamin supplementation.

Vitamins in psychiatry. Do they have a role?

Deficiencies of specific vitamins produce consistent symptoms of psychiatric disorder. Thiamine deficiency, which is common in alcoholism, can produce confusion and psychotic symptoms, in addition to neurological signs. Vitamin B12 and folate deficiency may contribute symptoms of disorientation, depression or psychosis; their measurement is a part of routine dementia work-ups. Pyridoxine deficiency results in seizures, although the effects of exogenously administered pyridoxine are not clearly understood in depression and anxiety - the disorders in which it is most frequently used clinically. The use of vitamins has been most prominent in psychiatry in the treatment of schizophrenia, where large doses of nicotinic acid were initially given alone and later combined with other vitamins and minerals. Several theoretical models were described to support the use of vitamins in schizophrenia. These included: the parallels of schizophrenia to the psychiatric symptoms of pellagra; hypotheses of a defect in adrenaline metabolism; and the accumulation of psychotoxic substances which produce psychotic symptoms. Initially, positive results were reported over 30 years ago, but have not been replicated by thorough investigations. An extensive series of comprehensive placebo-controlled trials failed to show efficacy for any of the vitamin therapies tested. Although clearly less effective than antipsychotic drug treatment, vitamin therapy is not without risks - adverse effects have been reported with nicotinic acid, pyridoxine and vitamin C.(ABSTRACT TRUNCATED AT 250 WORDS)