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Abstract：
BACKGROUND: Studies suggest that cerebrospinal fluid (CSF) levels of amyloid-β (Aβ)42 and Aβ40 present a circadian rhythm. However sustained sampling of large volumes of CSF with indwelling intrathecal catheters used in most of these studies might have affected CSF dynamics and thereby confounded the observed fluctuations in the biomarker levels.
METHODS: We included 38 individuals with either normal (N = 20) or abnormal (N = 18) CSF Aβ42/Aβ40 levels at baseline. CSF and plasma were collected at two visits separated by an average of 53 days with lumbar punctures and venipunctures performed either in the morning or evening. At the first visit, sample collection was performed in the morning for 17 participants and the order was reversed for the remaining 21 participants. CSF and plasma samples were analyzed for Alzheimer\' disease (AD) biomarkers, including Aβ42, Aβ40, GFAP, NfL p-tau181, p-tau217, p-tau231 and t-tau. CSF samples were also tested using mass spectrometry for 22 synaptic and endo-lysosomal proteins.
RESULTS: CSF Aβ42 (mean difference [MD], 0.21 ng/mL; p = 0.038), CSF Aβ40 (MD, 1.85 ng/mL; p < 0.001), plasma Aβ42 (MD, 1.65 pg/mL; p = 0.002) and plasma Aβ40 (MD, 0.01 ng/mL, p = 0.002) were increased by 4.2-17.0% in evening compared with morning samples. Further, CSF levels of 14 synaptic and endo-lysosomal proteins, including neurogranin and neuronal pentraxin-1, were increased by 4.5-13.3% in the evening samples (MDrange, 0.02-0.56 fmol/µl; p < 0.042). However, no significant differences were found between morning and evening levels for the Aβ42/Aβ40 ratio, different p-tau variants, GFAP and NfL. There were no significant interaction between sampling time and Aβ status for any of the biomarkers, except that CSF t-tau was increased (by 5.74%) in the evening samples compared to the morning samples in Aβ-positive (MD, 16.46 ng/ml; p = 0.009) but not Aβ-negative participants (MD, 1.89 ng/ml; p = 0.47). There were no significant interactions between sampling time and order in which samples were obtained.
CONCLUSIONS: Our findings provide evidence for diurnal fluctuations in Aβ peptide levels, both in CSF and plasma, while CSF and plasma p-tau, GFAP and NfL were unaffected. Importantly, Aβ42/Aβ40 ratio remained unaltered, suggesting that it is more suitable for implementation in clinical workup than individual Aβ peptides. Additionally, we show that CSF levels of many synaptic and endo-lysosomal proteins presented a diurnal rhythm, implying a build-up of neuronal activity markers during the day. These results will guide the development of unified sample collection procedures to avoid effects of diurnal variation for future implementation of AD biomarkers in clinical practice and drug trials.
METHODS: We included 38 individuals with either normal (N = 20) or abnormal (N = 18) CSF Aβ42/Aβ40 levels at baseline. CSF and plasma were collected at two visits separated by an average of 53 days with lumbar punctures and venipunctures performed either in the morning or evening. At the first visit, sample collection was performed in the morning for 17 participants and the order was reversed for the remaining 21 participants. CSF and plasma samples were analyzed for Alzheimer\' disease (AD) biomarkers, including Aβ42, Aβ40, GFAP, NfL p-tau181, p-tau217, p-tau231 and t-tau. CSF samples were also tested using mass spectrometry for 22 synaptic and endo-lysosomal proteins.
RESULTS: CSF Aβ42 (mean difference [MD], 0.21 ng/mL; p = 0.038), CSF Aβ40 (MD, 1.85 ng/mL; p < 0.001), plasma Aβ42 (MD, 1.65 pg/mL; p = 0.002) and plasma Aβ40 (MD, 0.01 ng/mL, p = 0.002) were increased by 4.2-17.0% in evening compared with morning samples. Further, CSF levels of 14 synaptic and endo-lysosomal proteins, including neurogranin and neuronal pentraxin-1, were increased by 4.5-13.3% in the evening samples (MDrange, 0.02-0.56 fmol/µl; p < 0.042). However, no significant differences were found between morning and evening levels for the Aβ42/Aβ40 ratio, different p-tau variants, GFAP and NfL. There were no significant interaction between sampling time and Aβ status for any of the biomarkers, except that CSF t-tau was increased (by 5.74%) in the evening samples compared to the morning samples in Aβ-positive (MD, 16.46 ng/ml; p = 0.009) but not Aβ-negative participants (MD, 1.89 ng/ml; p = 0.47). There were no significant interactions between sampling time and order in which samples were obtained.
CONCLUSIONS: Our findings provide evidence for diurnal fluctuations in Aβ peptide levels, both in CSF and plasma, while CSF and plasma p-tau, GFAP and NfL were unaffected. Importantly, Aβ42/Aβ40 ratio remained unaltered, suggesting that it is more suitable for implementation in clinical workup than individual Aβ peptides. Additionally, we show that CSF levels of many synaptic and endo-lysosomal proteins presented a diurnal rhythm, implying a build-up of neuronal activity markers during the day. These results will guide the development of unified sample collection procedures to avoid effects of diurnal variation for future implementation of AD biomarkers in clinical practice and drug trials.
摘要：
背景：研究表明，脑脊液（CSF）中淀粉样蛋白-β（Aβ）42和Aβ40的水平呈现昼夜节律。然而，在大多数这些研究中使用留置鞘内导管对大量CSF进行持续采样可能会影响CSF动力学，从而混淆了观察到的生物标志物水平的波动。
方法：我们纳入了38名基线时CSFAβ42/Aβ40水平正常（N=20）或异常（N=18）的个体。在两次访问时收集CSF和血浆，平均间隔53天，在早晨或晚上进行腰椎穿刺和静脉穿刺。在第一次访问时，17名参与者在上午进行了样本采集,其余21名参与者的顺序被颠倒.分析CSF和血浆样本的阿尔茨海默病（AD）生物标志物，包括Aβ42、Aβ40、GFAP、NfLp-tau181、p-tau217、p-tau231和t-tau。还使用质谱法测试了CSF样品中的22种突触和内溶酶体蛋白。
结果：CSFAβ42（平均差[MD]，0.21ng/mL；p=0.038），CSFAβ40（MD，1.85ng/mL；p<0.001)，血浆Aβ42（MD，1.65pg/mL；p=0.002）和血浆Aβ40（MD，0.01ng/mL,与早晨样本相比，晚上p=0.002）增加了4.2-17.0％。Further,14种突触和内溶酶体蛋白的CSF水平，包括神经颗粒蛋白和神经元正五聚蛋白-1，在晚间样本中增加了4.5-13.3%(MDrange，0.02-0.56fmol/μl；p<0.042）。然而,Aβ42/Aβ40比值在早晨和晚上水平之间没有发现显着差异，不同的p-tau变体，GFAP和NFL。任何生物标志物的采样时间和Aβ状态之间没有显著的相互作用，除了与Aβ阳性的早晨样本相比，夜间样本的CSFt-tau增加（5.74％）（MD，16.46ng/ml；p=0.009），但不是Aβ阴性参与者（MD，1.89ng/ml；p=0.47）。在采样时间和获得样品的顺序之间没有显著的相互作用。
结论：我们的发现为Aβ肽水平的昼夜波动提供了证据，在脑脊液和血浆中，而CSF和血浆p-tau，GFAP和NfL未受影响。重要的是,Aβ42/Aβ40比值保持不变，这表明它比单独的Aβ肽更适合在临床检查中实施。此外,我们发现许多突触和内溶酶体蛋白的CSF水平呈现昼夜节律，暗示白天神经元活动标记的积累。这些结果将指导统一样品收集程序的开发，以避免昼夜变化的影响，以便将来在临床实践和药物试验中实施AD生物标志物。
方法：我们纳入了38名基线时CSFAβ42/Aβ40水平正常（N=20）或异常（N=18）的个体。在两次访问时收集CSF和血浆，平均间隔53天，在早晨或晚上进行腰椎穿刺和静脉穿刺。在第一次访问时，17名参与者在上午进行了样本采集,其余21名参与者的顺序被颠倒.分析CSF和血浆样本的阿尔茨海默病（AD）生物标志物，包括Aβ42、Aβ40、GFAP、NfLp-tau181、p-tau217、p-tau231和t-tau。还使用质谱法测试了CSF样品中的22种突触和内溶酶体蛋白。
结果：CSFAβ42（平均差[MD]，0.21ng/mL；p=0.038），CSFAβ40（MD，1.85ng/mL；p<0.001)，血浆Aβ42（MD，1.65pg/mL；p=0.002）和血浆Aβ40（MD，0.01ng/mL,与早晨样本相比，晚上p=0.002）增加了4.2-17.0％。Further,14种突触和内溶酶体蛋白的CSF水平，包括神经颗粒蛋白和神经元正五聚蛋白-1，在晚间样本中增加了4.5-13.3%(MDrange，0.02-0.56fmol/μl；p<0.042）。然而,Aβ42/Aβ40比值在早晨和晚上水平之间没有发现显着差异，不同的p-tau变体，GFAP和NFL。任何生物标志物的采样时间和Aβ状态之间没有显著的相互作用，除了与Aβ阳性的早晨样本相比，夜间样本的CSFt-tau增加（5.74％）（MD，16.46ng/ml；p=0.009），但不是Aβ阴性参与者（MD，1.89ng/ml；p=0.47）。在采样时间和获得样品的顺序之间没有显著的相互作用。
结论：我们的发现为Aβ肽水平的昼夜波动提供了证据，在脑脊液和血浆中，而CSF和血浆p-tau，GFAP和NfL未受影响。重要的是,Aβ42/Aβ40比值保持不变，这表明它比单独的Aβ肽更适合在临床检查中实施。此外,我们发现许多突触和内溶酶体蛋白的CSF水平呈现昼夜节律，暗示白天神经元活动标记的积累。这些结果将指导统一样品收集程序的开发，以避免昼夜变化的影响，以便将来在临床实践和药物试验中实施AD生物标志物。
