Lipid metabolism in lactating ruminants

泌乳反刍动物的脂质代谢

• 批准号: RGPIN-2021-03383
• 负责人: Chouinard, Yvan
• 金额: $ 2.4万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=764729
• 关键词: Lipid; metabolism; lactating; ruminants

Linoleic acid (18:2 n-6) and alpha-linolenic acid (18:3 n-3) are essential nutrients in mammals. These fatty acids and their metabolites are involved in several biological functions, such as immune response, blood coagulation, vascular resistance, cell proliferation and differentiation, enzyme activities, and receptor expression. Ruminants, like other mammals, are not able to synthesize essential fatty acids (EFA); therefore, they must be obtained from feedstuffs. However, there is currently no defined EFA requirements for ruminants. Daily amounts required for lactating cows are hard to establish due to: i) fluctuating proportions of dietary EFA being biohydrogenated in the rumen, reducing their availability for absorption; and ii) varying quantities of n-6 and n-3 fatty acids being secreted in milk fat, which are therefore not available for animal metabolism. With adequate supply of EFA, 18:2 n-6 and 18:3 n-3 are desaturated and elongated to varying metabolites which are important regulators of physiological functions and gene expression. Studies have shown that consumption of greater quantities of EFA may have beneficial effects on hepatic metabolism and lactation performances and in lactating cows. Nevertheless, data are not conclusive enough to define specific intake requirements for an improved efficiency of these systems. The main objective of the proposed research program is to gain further insight into the metabolism of EFA in dairy ruminants. The hypothesis is that EFA supplies in lactating cows modulate hepatic metabolism and the delivery of nutrients to the mammary gland to support milk synthesis. The specific objectives are to: 1) explore the overall adaptations of liver and mammary tissues to EFA deficiency; 2) assess the role of 18:2 n-6 and 18:3 n-3 on animal physiology and lactation performance, when supplied individually or in combination; and 3) study the process of elongation, desaturation and ß-oxidation of EFA. Lactating cows will be fed an EFA-deficient diet. Biopsies will be harvested to determine the impacts on liver and mammary tissue transcriptomes, and blood samples will be collected to determined plasma metabolome. The same model of EFA-deficient cows will be used to further examine the impact of supplemental 18:2 n-6 and 18:3 n-3 on animal physiology. Abomasal infusion of these EFA will allow to study their metabolism (elongation, desaturation) and their effects on molecular and cellular functions, without the uncertainty related to varying rates of ruminal biohydrogenation. By creating a deficiency and controlling intake, biohydrogenation and secretion of EFA, the proposed research program has the potential to more precisely target the metabolic functions requiring 18:2 n-6, 18:3 n-3, or their metabolites. In the long run, this program will allow to define more precise dietary requirements of EFA in lactating ruminants.

亚油酸(18：2n-6)和α-亚麻酸(18：3n-3)是哺乳动物的必需营养物质。这些脂肪酸及其代谢产物参与多种生物学功能，如免疫反应、凝血、血管阻力、细胞增殖和分化、酶活性和受体表达。反刍动物和其他哺乳动物一样，不能合成必需脂肪酸；因此，它们必须从饲料中获得。然而，目前还没有针对反刍动物的明确的全民教育要求。很难确定哺乳奶牛的每日需要量，原因是：i)瘤胃内生物氢化的日粮全民脂肪酸比例波动，降低了它们的吸收利用率；ii)乳脂中分泌了不同数量的n-6和n-3脂肪酸，因此不能用于动物新陈代谢。在充足的EFA供应下，18：2n-6和18：3n-3被脱饱和和延长为不同的代谢物，这些代谢物是生理功能和基因表达的重要调节因素。研究表明，摄入更多的EFA可能会对肝脏代谢和哺乳性能以及哺乳期奶牛产生有益影响。然而，数据还不足以确定提高这些系统效率的具体摄入量要求。拟议研究计划的主要目标是进一步了解乳用反刍动物中全民脂肪酸的新陈代谢。假设是，在哺乳期奶牛中补充EFA可以调节肝脏新陈代谢，并将营养物质输送到乳腺，以支持牛奶的合成。具体目标是：1)探索肝脏和乳腺组织对EFA缺乏的整体适应；2)评估单独或联合供应18：2n-6和18：3n-3对动物生理和哺乳性能的影响；以及3)研究EFA的伸长、脱饱和和氧化过程。哺乳奶牛将被喂以缺乏全民教育的饮食。将采集活检以确定对肝脏和乳腺组织转录本的影响，并将采集血液样本以确定血浆代谢组。将使用相同的EFA缺乏奶牛模型来进一步研究补充18：2n-6和18：3n-3对动物生理的影响。皱胃注入这些EFA将允许研究它们的新陈代谢(伸长、去饱和)及其对分子和细胞功能的影响，而不会有与瘤胃生物氢化速率不同相关的不确定性。通过建立不足和控制全民脂肪酸的摄入、生物氢化和分泌，拟议的研究计划有可能更准确地针对需要18：2n-6、18：3n-3或其代谢物的代谢功能。从长远来看，该计划将允许更精确地定义哺乳反刍动物对全民教育的饮食要求。