Dietary and microbially derived fatty acids (FA) play important roles in gut mucosal inflammatory signaling, barrier function, and oxidative stress response. Nevertheless, little information is available about gastrointestinal FA profiles and receptor distribution in pigs, especially for long-chain FA (LCFA). Therefore, the present pilot study aimed to (1) investigate the gastrointestinal FA profiles; (2) link the luminal FA profiles to the mucosal expression of genes related to FA sensing and signaling; and (3) assess potential dietary effects on gut and systemic lipid metabolism in pigs. Gut, liver, and serum samples were obtained from barrows (13.1 ± 2.3 kg) fed diets containing either phytase (500 phytase units/kg diet) or cereals treated with 2.5% lactic acid (LA; n = 8/diet) for 18 d. Results showed gut regional and diet-related differences in luminal FA profiles and mucosal receptor expression, whereas diet little affected hepatic expression levels and serum lipids. Short-chain fatty acids (SCFA) increased from stomach, jejunum, and ileum to the cecum (P < 0.05), whereas LCFA were higher in stomach, cecum, and colon than in jejunum and ileum (P < 0.05). LA-treated cereals enhanced cecal acetate and butyrate, whereas phytase and LA treated cereals decreased the LCFA by 35.9% and 14.4%, respectively (P < 0.05). Gut regional differences suggested stronger signaling via FFAR1 expression in the ileum, and via FFAR2, FFAR4, and HCAR1 expression in cecum and colon (P < 0.05). Expression of AMPK, FASN, PPARG, SREBP1, and SREBP2 was higher in the cecum and colon compared with the small intestine (P < 0.05), with stronger sensing via FASN and SREBP2. Phytase decreased expression of FFAR2 and FFAR4, whereas it increased that of FFAR3 and MCT1 in the cecum (P < 0.05). LA-treated cereals raised cecal expression of FFAR3 and HCAR1 (P < 0.05). Pearson’s correlations (|r| > 0.35; P < 0.05) supported that FA receptor- and nuclear transcription factor-dependent pathways were involved in the mucosal regulation of gut incretin expression but differed across gut regions. In conclusion, results support regional differences in SCFA, lactate and LCFA sensing and absorption capacities in the small and large intestines of pigs. Effects of phytase and the LA-treated cereals on intestinal FA levels and signaling can be explained by differences in nutrient flows (e.g., phosphorus and carbohydrate fractions). This overview provides a solid basis for future intestinal FA sensing in pigs.

中文翻译：

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短链、中链和长链脂肪酸谱和信号传导对生长猪胃肠道谷物的膳食植酸酶和乳酸处理有反应

膳食和微生物来源的脂肪酸 (FA) 在肠道黏膜炎症信号传导、屏障功能和氧化应激反应中发挥重要作用。然而，关于猪胃肠道 FA 谱和受体分布的信息很少，尤其是长链 FA (LCFA)。因此，本试验性研究旨在 (1) 调查胃肠道 FA 谱；(2) 将腔 FA 谱与与 FA 传感和信号传导相关的基因的粘膜表达联系起来；(3) 评估日粮对猪肠道和全身脂质代谢的潜在影响。肠道、肝脏和血清样本取自饲喂含有植酸酶（500 植酸酶单位/kg 日粮）或用 2.5% 乳酸（LA；n = 8/日粮）处理 18 天的谷物的日粮（13.1 ± 2.3 kg） . 结果显示肠腔内 FA 谱和黏膜受体表达的肠道区域和饮食相关差异，而饮食对肝脏表达水平和血脂的影响很小。从胃、空肠和回肠到盲肠的短链脂肪酸（SCFA）增加（P < 0.05），而胃、盲肠和结肠的LCFA高于空肠和回肠（P < 0.05）。LA 处理的谷物增强了盲肠醋酸盐和丁酸盐，而植酸酶和 LA 处理的谷物分别使 LCFA 降低了 35.9% 和 14.4% (P < 0.05)。肠道区域差异表明通过回肠中 FFAR1 表达以及盲肠和结肠中 FFAR2、FFAR4 和 HCAR1 表达的信号更强（P < 0.05）。与小肠相比，盲肠和结肠中 AMPK、FASN、PPARG、SREBP1 和 SREBP2 的表达更高（P < 0.00）。0.05），通过 FASN 和 SREBP2 具有更强的感知能力。植酸酶降低了盲肠中FFAR2和FFAR4的表达，而增加了FFAR3和MCT1的表达（P < 0.05）。LA 处理的谷物提高了 FFAR3 和 HCAR1 的盲肠表达 (P < 0.05)。Pearson 的相关性 (|r| > 0.35; P < 0.05) 支持 FA 受体和核转录因子依赖性途径参与肠道肠促胰岛素表达的粘膜调节，但在肠道区域之间存在差异。总之，结果支持了猪小肠和大肠中 SCFA、乳酸和 LCFA 传感和吸收能力的区域差异。植酸酶和 LA 处理的谷物对肠道 FA 水平和信号传导的影响可以通过营养流动（例如磷和碳水化合物部分）的差异来解释。