Tryptophan deficiency and picolinic acid: effect on zinc metabolism and clinical manifestations of pellagra

The kynurenine pathway in chronic diseases: a compensatory mechanism or a driving force?

The kynurenine (KYN) pathway (KP) of tryptophan (TRP) metabolism is dysregulated in inflammation-driven pathologies including oncological and brain diseases [e.g., multiple sclerosis (MS), depression] and thus is a promising therapeutic target. Both pathological and compensatory mechanisms underlie disease-associated KP activation. There is growing evidence for bioenergetic roles of certain KP metabolites such as kynurenic acid (KA), or quinolinic acid (QA) as an NAD⁺ precursor, which may explain its frequently observed 'pathological' overactivation. Disease- and tissue-specific aspects, negative feedback on inflammatory signals, and the balance of downstream metabolites are likely to be decisive factors in the interpretation of an imbalanced KP. Therapeutic strategies should consider the compensatory actions and bioenergetic roles of KP metabolites to successfully design future theragnostic approaches aimed at attenuating disease progression.

Role of Nicotinamide Adenine Dinucleotide and Related Precursors as Therapeutic Targets for Age-Related Degenerative Diseases: Rationale, Biochemistry, Pharmacokinetics, and Outcomes

Significance: Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide that serves as an essential cofactor and substrate for a number of critical cellular processes involved in oxidative phosphorylation and ATP production, DNA repair, epigenetically modulated gene expression, intracellular calcium signaling, and immunological functions. NAD+ depletion may occur in response to either excessive DNA damage due to free radical or ultraviolet attack, resulting in significant poly(ADP-ribose) polymerase (PARP) activation and a high turnover and subsequent depletion of NAD+, and/or chronic immune activation and inflammatory cytokine production resulting in accelerated CD38 activity and decline in NAD+ levels. Recent studies have shown that enhancing NAD+ levels can profoundly reduce oxidative cell damage in catabolic tissue, including the brain. Therefore, promotion of intracellular NAD+ anabolism represents a promising therapeutic strategy for age-associated degenerative diseases in general, and is essential to the effective realization of multiple benefits of healthy sirtuin activity. The kynurenine pathway represents the de novo NAD+ synthesis pathway in mammalian cells. NAD+ can also be produced by the NAD+ salvage pathway. Recent Advances: In this review, we describe and discuss recent insights regarding the efficacy and benefits of the NAD+ precursors, nicotinamide (NAM), nicotinic acid (NA), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN), in attenuating NAD+ decline in degenerative disease states and physiological aging. Critical Issues: Results obtained in recent years have shown that NAD+ precursors can play important protective roles in several diseases. However, in some cases, these precursors may vary in their ability to enhance NAD+ synthesis via their location in the NAD+ anabolic pathway. Increased synthesis of NAD+ promotes protective cell responses, further demonstrating that NAD+ is a regulatory molecule associated with several biochemical pathways. Future Directions: In the next few years, the refinement of personalized therapy for the use of NAD+ precursors and improved detection methodologies allowing the administration of specific NAD+ precursors in the context of patients' NAD+ levels will lead to a better understanding of the therapeutic role of NAD+ precursors in human diseases.

Nicotinamide's Ups and Downs: Consequences for Fertility, Development, Longevity and Diseases of Poverty and Affluence

To further explore the role of dietary nicotinamide in both brain development and diseases, particularly those of ageing. Articles cover neurodegenerative disease and cancer. Also discussed are the effects of nicotinamide, contained in meat and supplements and derived from symbionts, on the major transitions of disease and fertility from ancient times up to the present day. A key role for the tryptophan - NAD 'de novo' and immune tolerance pathway are discussed at length in the context of fertility and longevity and the transitions from immune paresis to Treg-mediated immune tolerance and then finally to intolerance and their associated diseases. Abstract: Nicotinamide in human evolution increased cognitive power in a positive feedback loop originally involving hunting. As the precursor to metabolic master molecule NAD it is, as vitamin B3, vital for health. Paradoxically, a lower dose on a diverse plant then cereal-based diet fuelled population booms from the Mesolithic onwards, by upping immune tolerance of the foetus. Increased tolerance of risky symbionts, whether in the gut or TB, that excrete nicotinamide co-evolved as buffers for when diet was inadequate. High biological fertility, despite disease trade-offs, avoided the extinction of Homo sapiens and heralded the dawn of a conscious, creative, and pro-fertility culture. Nicotinamide equity now would stabilise populations and prevent NAD-based diseases of poverty and affluence.

Nicotinamide adenine dinucleotide and its related precursors for the treatment of Alzheimer's disease

PURPOSE OF REVIEW

The current review discusses the biology and metabolism of the essential pyridine nucleotide nicotinamide adenine dinucleotide (NAD+) in the central nervous system. We also review recent work suggesting important neuroprotective effects that may be associated with the promotion of NAD+ levels through NAD+ precursors against Alzheimer's disease.

RECENT FINDINGS

Perturbations in the physiological homoeostatic state of the brain during the ageing process can lead to impaired cellular function, and ultimately leads to loss of brain integrity and accelerates cognitive and memory decline. Increased oxidative stress has been shown to impair normal cellular bioenergetics and enhance the depletion of the essential nucleotides NAD+ and ATP. NAD+ and its precursors have been shown to improve cellular homoeostasis based on association with dietary requirements, and treatment and management of several inflammatory and metabolic diseases in vivo. Cellular NAD+ pools have been shown to be reduced in the ageing brain, and treatment with NAD+ precursors has been hypothesized to restore these levels and attenuate disruption in cellular bioenergetics.

SUMMARY

NAD+ and its precursors may represent an important therapeutic strategy to maintain optimal cellular homoeostatic functions in the brain. NAD+ precursors are available in a variety of foods and may be translated to the clinic in the form of supplements.

Effects of pre- and postnatal exposure to chromium picolinate or picolinic acid on neurological development in CD-1 mice

Chromium picolinate, Cr(pic)3, a popular dietary supplement marketed as an aid in fat loss and lean muscle gain, has also been suggested as a therapy for women with gestational diabetes. The current study investigated the effects of maternal exposure to Cr(pic)3 and picolinic acid during gestation and lactation on neurological development of the offspring. Mated female CD-1 mice were fed diets from implantation through weaning that were either untreated or that contained Cr(pic)3 (200 mg kg(-1) day(-1)) or picolinic acid (174 mg kg(-1) day(-1)). A comprehensive battery of postnatal tests was administered, including a modified Fox battery, straight-channel swim, open-field activity, and odor-discrimination tests. Pups exposed to picolinic acid tended to weigh less than either control or Cr(pic)3-exposed pups, although the differences were not significant. Offspring of picolinic acid-treated dams also appeared to display impaired learning ability, diminished olfactory orientation ability, and decreased forelimb grip strength, although the differences among the treatment groups were not significant. The results indicate that there were no significant effects on the offspring with regard to neurological development from supplementation of the dams with either Cr(pic)3 or picolinic acid.

Characterization of the low mol. wt zinc-binding ligand from rat small intestine by comparison to the organic zinc-binding ligands

1. 65Zn complexes of picolinate (PA), citrate (CA), L-histidine (L-his), arachidonic acid (AA) or low mol. wt zinc-binding ligand from rat intestine (LMW-ZBL) gave 65Zn eluting peak fraction numbers of 53, 53, 56, 59 and 59 respectively, in a Sephadex G-75 column chromatography. 2. The 65Zn eluting peak fraction numbers with CA, L-his, PA, prostaglandin (PG)E2, AA, no ligand, arachidonate (AT) or LMW-ZBL were 49, 50, 54, 55, 58, 64, 75 and 76 respectively in a Sephadex G-25 column chromatography. 3. In a Sephadex G-15 column chromatography, the 65Zn eluting peak fraction numbers with CA, PGE2, AA, L-his, LMW-ZBL or PA were 49, 50, 51, 52, 52 and 55 respectively. 4. The LMW-ZBL in rat small intestine appears to be an AA-like substance.