36 DECEMBER 2014 • WORLD AQUACULTURE • WWW.WAS.ORG Controlling Inflammation with Flavanoids—An Option for Future Aquafeeds Malte Lohölter, Susanne Kirwan and Bernhard Eckel With annual growth rates of approximately 10 percent throughout the last five decades, the global aquaculture sector is the fastest growing food-producing industry in the world (Pettersson 2010). Despite great past and present success, aquaculture is facing diverse challenges, including a need for increased productivity and efficiency while simultaneously implementing further replacement of traditional feed ingredients derived from marine fisheries. Achieving these apparently opposite targets will be ambitious and likely to have unexpected side-effects that need to be taken into account in expedient diet formulation. Current research indicates processes subsumed as inflammation may be among these detrimental side-effects, leading to suboptimal feed efficiency, animal growth and eventually affecting profitability of the production system. The present article summarizes current knowledge, providing a glimpse at the potential future impact of inflammation on cultured aquatic species, while discussing existing and conceivable solutions. Impacts of Inflammation Inflammation is often imprecisely considered a synonym for infection but should be understood as a complex stereotypic response of the body to damage of its tissues or undesired chemical (reactive oxidants, acids, lyes, toxins), physical (foreign objects, radiation, heat, cold) and biological (viruses, bacteria) stimuli (Weiss 2008). The main objective of the processes subsumed as inflammation is to eliminate the damage, stop the spread of injury and restore the functionality of the affected regions. The body responds to the onset of inflammation with molecular changes in gene expression and diverse reactions of the immune system. In the initial reaction, affected tissues are subjected to an increased blood flow, followed by altered concentrations of different plasma proteins and white blood cells. The liver responds with increased production of specific proteins (so-called acute-phase proteins) that are capable of destroying or inhibiting microbes and subsequently giving a negative feedback to the inflammatory response to down-regulate the physiological response to the stimuli. At the molecular level, inflammatory processes are regulated by a protein complex, NF-ĸB, which is found in its inactive form in the liquid phase of cells. As summarized in Figure 1, inflammation can ultimately lead to impaired liver function, anorexia, pain and muscle degradation. But what happens if the defense mechanisms of the organism are not able to fully limit the inflammation to its transient acute form (lack of healing)? So-called chronic inflammation can occur and lead to the development of a variety of disorders. In contrast to acute inflammation, which is typically characterized by the five signs of pain, heat, redness, swelling and loss of function, chronic inflammation is often less visible and can affect apparently healthy animals, which are well supplied with all required nutrients, according to current recommendations. In humans, chronic inflammation is known to be related to cancer, allergic reactions, atherosclerosis and myopathies. As a general consequence of inflammation, the physiological priority is shifted toward healing and cell protection, meaning that a considerable amount of dietary energy and protein is used to control these processes and is no longer available for tissue and muscle growth. Thus, animals are no longer able to reach their genetic potential and farmers are likely to experience economic losses. The Future Situation Production losses associated with inflammation are likely to increase in future aquaculture. Although knowledge and awareness TOP, FIGURE 1. Physiological effects related to inflammation. BOTTOM, FIGURE 2. Dietary inclusion of fishmeal in aquafeeds from 1995 to 2010 (Redrawn from Tacon et al. 2011).
RkJQdWJsaXNoZXIy MjExNDY=