Effects of mycotoxins on animal health: from oxidative stress to gene expressions | Vpliv mikotoksinov na zdravje zivali: od oksidativnega stresa do ekspresije genov

Mycotoxin contamination of the feed and food is a global problem. The major mycotoxin-producing fungal genus are Aspergillus, Fusarium and Penicillium. The primary classes of mycotoxins are aflatoxins, zearalenones, trichothecenes, fumonisins, ochratoxins and ergot alkaloids. However, one of the most common grain-contaminating genus of fungi, Fusarium spp., is also capable of producing other toxic secondary metabolites the so-called emerging mycotoxins such as fusaproliferin, beauvericin, enniatins, and moniliformin. There are several unresolved questions in this regard. Firstly, more than 25 % of world grain production is contaminated by mycotoxins. In particular, Fusarium mycotoxins (so called field mycotoxins) contaminate up to 100 % of the grain. Since these mycotoxins are coming from the field it is difficult to deal with them and various technological approaches including plant selection for mycotoxin resistance did not produce any significant results. Secondly, in nature there are more than 300 mycotoxins, but analytical techniques for routine mycotoxins analysis are developed only for about 30 major mycotoxins. Therefore, if there is a conclusion from the analytical lab that 'the mycotoxins are not found' this means that 10-30 mycotoxins analyzed were not found. As for others, there is no answer. Thirdly, sampling for mycotoxins analysis is extremely difficult and is an important source of errors. Fourthly, there are no safe levels of mycotoxins, because of synergistic interactions of many mycotoxins: several mycotoxins in low concentrations could cause more problems than a single mycotoxin at higher dose. Recent results show that in many cases membrane-active properties of various mycotoxins determine their toxicity. Indeed, incorporation of mycotoxins into membrane structures causes various detrimental changes. These changes are associated with alteration of fatty acid composition of the membrane structures and with peroxidation of long chain PUFAs inside membranes. This ultimately damages membrane receptors, causing alterations in second messenger systems; inactivation of a range of membrane-binding enzymes responsible for regulation of important pathways. Finally, this causes alterations in membrane permeability, flexibility and other important characteristics determining membrane function. Detrimental effects of mycotoxins on DNA, RNA and protein synthesis together with pro-apoptotic action further compromise important metabolic pathways. Consequently, changes in physiological functions including growth, development and reproduction occur. An importance of oxidative stress and lipid peroxidation in all these processes is confirmed by protective effects of natural antioxidants against mycotoxin toxicity. However, protective effects of antioxidants including selenium are of limited value and a combination of mycotoxin binders with natural antioxidants could be the next step in preventing damaging effects of mycotoxins in animal and poultry production.