Radical Response: Effects of Heat Stress-Induced Oxidative Stress on Lipid Metabolism in the Avian Liver

Abstract

Lipid metabolism in avian species places unique demands on the liver in comparison to most mammals. The avian liver synthesizes the vast majority of fatty acids that provide energy and support cell membrane synthesis throughout the bird. Egg production intensifies demands to the liver as hepatic lipids are needed to create the yolk. The enzymatic reactions that underlie de novo lipogenesis are energetically demanding and require a precise balance of vitamins and cofactors to proceed efficiently. External stressors such as overnutrition or nutrient deficiency can disrupt this balance and compromise the liver’s ability to support metabolic needs. Heat stress is an increasingly prevalent environmental factor that impairs lipid metabolism in the avian liver. The effects of heat stress-induced oxidative stress on hepatic lipid metabolism are of particular concern in modern commercial chickens due to the threat to global poultry production. Chickens are highly vulnerable to heat stress because of their limited capacity to dissipate heat, high metabolic activity, high internal body temperature, and narrow zone of thermal tolerance. Modern lines of both broiler (meat-type) and layer (egg-type) chickens are especially sensitive to heat stress because of the high rates of mitochondrial metabolism. While this oxidative metabolism supports growth and egg production, it also yields oxidative stress that can damage mitochondria, cellular membranes and proteins, making the birds more vulnerable to other stressors in the environment. Studies to date indicate that oxidative and heat stress interact to disrupt hepatic lipid metabolism and compromise performance and well-being in both broilers and layers. The purpose of this review is to summarize the impact of heat stress-induced oxidative stress on lipid metabolism in the avian liver. Recent advances that shed light on molecular mechanisms and potential nutritional/managerial strategies to counteract the negative effects of heat stress-induced oxidative stress to the avian liver are also integrated.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

“…The mechanisms of genistein action on chronic liver damage due to alcohol have also been recently identified. Genistein increases the lipid oxidation and peroxidation markers [heme oxygenase-1 (HO-1), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GPX)] that had been reduced by alcohol but decreased the inflammatory cytokines (NF-κB, p65, TGF-1β, COX-2, MCP-1, TNF-α, and IL-6) that had been increased by alcohol (Figure 7) [78,117,118]. Genistein provides antioxidant and anti-inflammatory activities to effectively protect the liver against chronic damage due to alcohol.…”

Heat Stress and Feed Restriction Distinctly Affect Performance, Carcass and Meat Yield, Intestinal Integrity, and Inflammatory (Chemo)Cytokines in Broiler Chickens

“…Global warming is threatening all kinds of life on earth, especially avian species, which are highly susceptible to heat stress (HS) due to the lack of sweat glands and higher core body temperatures compared to mammals (42 • C compared to 37 • C) (Warren et al, 2018;Emami et al, 2020b). Demand for poultry meat is on the rise and poultry production is expected to increase more than double by 2050 (O'keefe, 2014).…”

“…Demand for poultry meat is on the rise and poultry production is expected to increase more than double by 2050 (O'keefe, 2014). However, several factors, including HS, negatively impact the efforts of the poultry industry to meet the high demands by eliciting physiological, behavioral, and production changes in poultry (Emami et al, 2020b;Wasti et al, 2020).…”

Effect of dietary saffron (Crocus sativus) petal extract on growth performance, blood biochemical indices, antioxidant balance, and immune responses of broiler chickens reared under heat stress conditions

“…The production rate of radicals is inversely related to the electron transfer rate in the mitochondrial respiratory chain. Chronic heat stress, via reducing the expression of antioxidant enzymes and reducing the body's antioxidant reserves, reduces the metabolic capacity of mitochondria, which increases the accumulation of oxygen free radicals and disrupts the oxidative balance leading to oxidative stress (Emami et al 2020). It has been shown that exposing broiler chickens to HS reduced the activity of antioxidant enzymes and the level of non-enzymatic antioxidants, whereas stimulated the production of free radicals (Sahin et al 2004;Hosseini-Vashan et al 2016;Safdari-Rostamabad et al 2017).…”