INRA, UMR1213 Herbivores, Saint-Genès-ChampanelleF-63122, France.
Clermont Université, VetAgro Sup, UMR1213 Herbivores, BP 10448, Clermont-FerrandF-63000, France.
Animal. 2020 Jul;14(7):1422-1437. doi: 10.1017/S1751731119003410. Epub 2020 Jan 23.
For their glucose supply, ruminants are highly dependent on the endogenous synthesis in the liver, but despite the numerous studies that evaluated hepatic glucose production, very few simultaneously measured hepatic glucose production and uptake of all precursors. As a result, the variability of precursor conversion into glucose in the liver is not known. The present study aimed at investigating by meta-analysis the relationships between hepatic glucose net release and uptake of precursors. We used the FLuxes of nutrients across Organs and tissues in Ruminant Animals database, which gathers international results on net nutrient fluxes at splanchnic level measured in catheterized animals. Response equations were developed for intakes up to 41 g DM intake/kg BW per day of diets varying from 0 to 100 g of concentrate/100 g DM in the absence of additives. The net hepatic uptake of propionate, α-amino-N and l-lactate was linearly and better related to their net portal appearance (NPA) than to their afferent hepatic flux. Blood flow data were corrected for lack of deacetylation of the para-aminohippuric acid, and this correction was shown to impact the response equations. To develop response equations between the availability of precursors (portal appearance and hepatic uptake) and net glucose hepatic release, missing data on precursor fluxes were predicted from dietary characteristics using previously developed response equations. Net hepatic release of glucose was curvilinearly related to hepatic supply and uptake of the sum of precursors, suggesting a lower conversion rate of precursors at high precursor supply. Factors of variation were explored for the linear portion of this relationship, which applied to NPA of precursors ranging from 0.99 to 9.60 mmol C/kg BW per h. Hepatic release of glucose was shown to be reduced by the portal absorption of glucose from diets containing bypass starch and to be increased by an increased uptake of β-hydroxybutyrate indicative of higher body tissue mobilization. These relationships were affected by the physiological status of the animals. In conclusion, we established equations that quantify the net release of glucose by the liver from the net availability of precursors. They provide a quantitative overview of factors regulating hepatic glucose synthesis in ruminants. These equations can be linked with the predictions of portal absorption of nutrients from intake and dietary characteristics, and provide indications of glucose synthesis from dietary characteristics.
对于葡萄糖供应，反刍动物高度依赖肝脏内源性合成，但尽管有许多研究评估了肝葡萄糖生成，很少有研究同时测量所有前体的肝葡萄糖生成和摄取。因此，肝脏中前体转化为葡萄糖的可变性尚不清楚。本研究旨在通过荟萃分析研究肝葡萄糖净释放与前体摄取之间的关系。我们使用了反刍动物器官和组织营养通量数据库，该数据库汇集了导管动物测量的内脏水平净营养通量的国际结果。为摄入量高达 41 g DM 摄入/kg BW/天的日粮开发了响应方程，这些日粮的范围从 0 到 100 g 浓缩物/100 g DM，且不含添加剂。丙酸盐、α-氨基-N 和 l-乳酸的净肝摄取与它们的净门静脉出现（NPA）呈线性关系，且比它们的传入肝通量更好地相关。血液流量数据针对对氨基马尿酸的脱乙酰化不足进行了校正，并且该校正会影响响应方程。为了在前体（门静脉出现和肝摄取）可用性与净葡萄糖肝释放之间建立响应方程，使用以前开发的响应方程从膳食特征预测了前体通量的缺失数据。葡萄糖的净肝释放与前体总和的肝供应和摄取呈曲线关系，表明在前体供应高时前体的转化率较低。探索了该关系线性部分的变异因素，该部分适用于前体 NPA 范围为 0.99 至 9.60 mmol C/kg BW/小时。结果表明，含有旁路淀粉的日粮中门静脉吸收葡萄糖会降低葡萄糖的肝释放，而增加 β-羟丁酸的摄取会增加，这表明更高的组织动员。这些关系受到动物生理状态的影响。总之，我们建立了定量描述肝脏从前体净可用性中释放葡萄糖的方程。它们提供了反刍动物肝葡萄糖合成调节的定量概述。这些方程可以与从摄入量和膳食特征预测门静脉吸收营养素联系起来，并提供从膳食特征预测葡萄糖合成的指标。
