Infantile diarrhea is a serious public health problem around worldwide and results in millions of deaths each year. The levels and sources of dietary protein are potential sources of diarrhea, but the relationship between the pathogenesis causes of infantile diarrhea and protein intake remains poorly understood. Many studies have indicated that the key to understanding the relationship between the protein in the diet and the postweaning diarrhea of piglets is to explore the influences of protein sources and levels on the mammalian digestion system. The current study was designed to control diarrhea control by choosing different protein levels in the diet and aimed at providing efficient regulatory measures for infantile diarrhea by controlling the protein levels in diets using a postweaning piglets model. To avoid influences from other protein sources, casein was used as the only protein source in this study. Fourteen piglets (, weaned at 28 d) were randomly allotted to two dietary treatments: a control group (Cont, containing 17% casein) and a high protein group (HP, containing 30% casein). The experiment lasted for two weeks and all animals were free to eat and drink water ad libitum. The diarrhea score (; ) and growth performance were recorded daily. The results showed that the piglets in HP group had persistent diarrhea during the whole study, while no diarrhea was noticed in the control groups. Also, the feed intake and body weights were reduced in the HP groups compared with the other group (). The diarrhea-related mRNA abundances were analyzed by real-time PCR; the results showed that HP treatment markedly decreased the expression of aquaporin (AQP, ) and the tight junction protein (P<0.05), but increased inflammatory cytokines () than those in control group. In addition, the Adenosine 5-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway () was inhibited in the HP group. Intestinal microbiota was tested by 16S sequencing, and we found that the HP group had a low diversity compared the other group. In conclusion, despite being highly digestible, a high casein diet induced postweaning diarrhea and reduced the growth performance of the postweaning piglets. Meanwhile, AQP, tight junction protein, and intestinal immune were compromised. Thus, the mechanism of how a highly digestible protein diet induces diarrhea might be associated with the AMPK signaling pathway and intestinal microbiome.

中文翻译：

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断奶仔猪模型中的蛋白质水平和婴儿腹泻。

婴儿腹泻是全球范围内的严重公共卫生问题，每年导致数百万人死亡。膳食蛋白质的水平和来源是腹泻的潜在来源，但婴儿腹泻的病因与蛋白质摄入之间的关系仍然知之甚少。许多研究表明，了解日粮中蛋白质与仔猪断奶后腹泻之间关系的关键是探索蛋白质来源和水平对哺乳动物消化系统的影响。当前的研究旨在通过选择日粮中不同的蛋白质水平来控制腹泻，并且旨在通过使用断奶后仔猪模型控制日粮中的蛋白质水平来为婴儿腹泻提供有效的调节措施。为了避免受到其他蛋白质来源的影响，在本研究中使用酪蛋白作为唯一的蛋白质来源。十四头小猪（，在第28天断奶）被随机分配给两种饮食疗法：对照组（Cont，含17％酪蛋白）和高蛋白组（HP，含30％酪蛋白）。实验持续了两个星期，所有动物自由随意进食和饮水。腹泻评分（; ）和生长性能每天都记录下来。结果显示，HP组的仔猪在整个研究过程中持续腹泻，而对照组中未观察到腹泻。此外，与其他组相比，HP组的采食量和体重均降低了（）。通过实时荧光定量PCR分析腹泻相关的mRNA丰度。结果表明，HP处理显着降低了水通道蛋白（AQP，）和紧密连接蛋白（P <0.05），但炎症细胞因子增加（），而不是对照组。此外，腺苷5 -一磷酸（AMP）激活的蛋白激酶（AMPK）信号传导途径（）在HP组中被抑制。肠道菌群通过16S测序进行了测试，我们发现HP组与其他组相比具有较低的多样性。总之，尽管高易消化的酪蛋白饮食容易引起断奶后腹泻，但降低了断奶后仔猪的生长性能。同时，AQP，紧密连接蛋白和肠道免疫受到损害。因此，高度易消化的蛋白质饮食如何引起腹泻的机制可能与AMPK信号通路和肠道微生物组有关。