Background: Bile acid (BA) and short chain fatty acid (SCFA) production is affected by diet and microbial metabolism. These metabolites may play important roles in human carcinogenesis. Methods: We used a fully quantitative targeted LC-MS/MS system to measure serum and fecal BA and SCFA concentrations in 136 Costa Rican adults at study baseline and 6-months. We randomly selected 50 participants and measured their baseline samples in duplicate. Our objective was to evaluate: Technical reproducibility; 6-month temporal variability; and concordance between sample type collected from the same individual at approximately the same time. Results: Technical reproducibility was excellent, with intraclass correlation coefficients (ICC) ≥0.83 for all BAs except serum tauroursodeoxycholic acid (ICC = 0.72) and fecal glycolithocholic acid (ICC = 0.66) and ICCs ≥0.81 for all SCFAs except serum 2-methylbutyric acid (ICC = 0.56) and serum isobutyric acid (ICC = 0.64). Temporal variability ICCs were generally low, but several BAs (i.e., deoxycholic, glycoursodeoxycholic, lithocholic, taurocholic, and tauroursodeoxycholic acid) and SCFAs (i.e., 2-methylbutyric, butyric, propionic, and valeric acid) had 6-month ICCs ≥0.44. The highest degree of concordance was observed for secondary and tertiary BAs. Conclusions: Serum and fecal BAs and SCFAs were reproducibly measured. However, 6-month ICCs were generally low, indicating that serial biospecimen collections would increase statistical power in etiologic studies. The low concordance for most serum and fecal metabolites suggests that consideration should be paid to treating these as proxies. Impact: Our findings will inform the design and interpretation of future human studies on associations of BAs, SCFAs, and potentially other microbial metabolites, with disease risk.

中文翻译：

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基于人群的研究中血清和粪便胆汁酸和短链脂肪酸的可重复性、时间变异性和一致性

背景：胆汁酸 (BA) 和短链脂肪酸 (SCFA) 的产生受饮食和微生物代谢的影响。这些代谢物可能在人类致癌过程中发挥重要作用。方法：我们使用完全定量的靶向 LC-MS/MS 系统测量 136 名哥斯达黎加成年人在研究基线和 6 个月时的血清和粪便 BA 和 SCFA 浓度。我们随机选择了 50 名参与者，并一式两份测量了他们的基线样本。我们的目标是评估： 技术再现性；6 个月的时间变化；以及大约在同一时间从同一个人收集的样本类型之间的一致性。结果：技术重现性非常好，除血清牛磺熊去氧胆酸 (ICC = 0.72) 和粪便乙醇石胆酸 (ICC = 0. 66) 和所有 SCFA 的 ICC ≥ 0.81，除了血清 2-甲基丁酸 (ICC = 0.56) 和血清异丁酸 (ICC = 0.64)。时间变异性 ICC 通常较低，但一些 BA（即脱氧胆酸、糖熊去氧胆酸、石胆酸、牛磺胆酸和牛磺熊去氧胆酸）和 SCFA（即 2-甲基丁酸、丁酸、丙酸和戊酸）的 6 个月 ICC ≥0.44。二级和三级 BA 的一致性最高。结论：可重复测量血清和粪便 BA 和 SCFA。然而，6 个月的 ICC 通常较低，这表明连续收集生物样本将增加病因学研究的统计功效。大多数血清和粪便代谢物的低一致性表明应考虑将它们视为代理。影响：