Emami Nima K, Jung Usuk, Voy Brynn, Dridi Sami
Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA.
College of Arts & Sciences, University of Tennessee, Knoxville, TN 37996, USA.
Antioxidants (Basel). 2020 Dec 30;10(1):35. doi: 10.3390/antiox10010035.
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.
与大多数哺乳动物相比，鸟类的脂质代谢对肝脏有独特的要求。鸟类肝脏合成了绝大多数脂肪酸，这些脂肪酸为鸟类提供能量并支持细胞膜的合成。产蛋会增加对肝脏的需求，因为需要肝脏脂质来形成蛋黄。从头脂肪生成所依据的酶促反应需要大量能量，并且需要维生素和辅因子的精确平衡才能有效进行。诸如营养过剩或营养缺乏等外部应激源会破坏这种平衡，并损害肝脏支持代谢需求的能力。热应激是一种日益普遍的环境因素，会损害鸟类肝脏中的脂质代谢。由于对全球家禽生产构成威胁，热应激诱导的氧化应激对肝脏脂质代谢的影响在现代商业鸡中尤为令人担忧。鸡因散热能力有限、代谢活动高、体内体温高以及热耐受范围窄，极易受到热应激的影响。现代肉鸡（肉用型）和蛋鸡（蛋用型）品系由于线粒体代谢率高，对热应激尤其敏感。虽然这种氧化代谢支持生长和产蛋，但它也会产生氧化应激，从而损害线粒体、细胞膜和蛋白质，使鸡更容易受到环境中其他应激源的影响。迄今为止的研究表明，氧化应激和热应激相互作用，会破坏肝脏脂质代谢，并损害肉鸡和蛋鸡的生产性能和健康状况。本综述的目的是总结热应激诱导的氧化应激对鸟类肝脏脂质代谢的影响。还整合了最近在分子机制方面的进展以及潜在的营养/管理策略，以抵消热应激诱导的氧化应激对鸟类肝脏的负面影响。
