Influence of Dietary Compounds on Arsenic Metabolism and Toxicity. Part I-Animal Model Studies.

Monika Sijko,Lucyna Kozłowska

doi:10.3390/toxics9100258

Abstract

Population and laboratory studies indicate that exposure to various forms of arsenic (As) is associated with many adverse health effects; therefore, methods are being sought out to reduce them. Numerous studies focus on the effects of nutrients on inorganic As (iAs) metabolism and toxicity, mainly in animal models. Therefore, the aim of this review was to analyze the influence of methionine, betaine, choline, folic acid, vitamin B2, B6, B12 and zinc on the efficiency of iAs metabolism and the reduction of the severity of the whole spectrum of disorders related to iAs exposure. In this review, which includes 58 (in vivo and in vitro studies) original papers, we present the current knowledge in the area. In vitro and in vivo animal studies showed that methionine, choline, folic acid, vitamin B2, B12 and zinc reduced the adverse effects of exposure to iAs in the gastrointestinal, urinary, lymphatic, circulatory, nervous, and reproductive systems. On the other hand, it was observed that these compounds (methionine, choline, folic acid, vitamin B2, B12 and zinc) may increase iAs metabolism and reduce toxicity, whereas their deficiency or excess may impair iAs metabolism and increase iAs toxicity. Promising results of in vivo and in vitro on animal model studies show the possibility of using these nutrients in populations particularly exposed to As.

Highlights

The metabolism of inorganic arsenic was mainly analyzed in animal model studies, in vivo and in vitro
Numerous studies where the effects of folic acid and zinc have been analyzed allow one to draw some conclusions in terms of the role of these nutrients in inorganic arsenic (iAs) metabolism and the adverse effect reduction
Folic acid and zinc supplementation improved iAs metabolism and reduced adverse changes induced by iAs in many systems: digestive, urinary, cardiovascular, lymphatic, nervous and reproductive

Summary

Introduction

The metabolism of inorganic arsenic (iAs) was mainly analyzed in animal model studies, in vivo and in vitro. The iAs metabolism may vary considerably depending on the animal species [1]. The iAs metabolism involves alternate reactions of methylation and reduction to MMA (monomethylarsonic acid), DMA, and these forms it are excreted by the kidneys. The major form of iAs excretion is DMA, and in humans, it can be excreted unchanged and as MMA and DMA [4–6]. The methylation reactions of iAs are catalyzed by an enzyme—arsenic (+3 oxidation state) methyltransferase [7]. Various dietary compounds are involved in the OCM, mainly as methyl group donors: methionine, choline, betaine, folic acid, and cofactors of the reaction—e.g., vitamin B2, B6, B12 and zinc (Figure 1) [8]

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