In Vivo Monitoring of Amino Acid Biomarkers from Inguinal Adipose Tissue Using Online Microdialysis-Capillary Electrophoresis

Abstract

We have developed an online, high-throughput, microdialysis-capillary electrophoresis (MD-CE) assay for measuring the in vivo dynamics of amino acid biomarkers of metabolism in adipose tissue. Microdialysis probes were implanted into the inguinal adipose tissue depot of C57BL6 mice. The probe location and integrity were verified following each experiment, demonstrating our ability to accurately target the inguinal adipose tissue depot without damaging the probe. The relative concentrations of small molecule bioamines were measured in adipose tissue every 22 s. Arginine, lysine, isoleucine, leucine, methionine, phenylalanine, valine, GABA, glutamine, alanine, glycine and taurine were separated and detected at concentrations significantly higher than the assay LOD. The relative abundances of these analytes were found to be reproducible between mice. The capability of the online MD-CE assay to record dynamic, in vivo changes was assessed by administering an insulin stimulation via tail vein injection. Valine concentrations increased by 40% in response to insulin exposure, while alanine increased by 46% and taurine increased by 37%. Following the initial increase, the amino acid concentrations remained significantly elevated for an extended period (p < 0.001).

Advances in the Determination of Nonprotein Amino Acids in Foods and Biological Samples by Capillary Electrophoresis

“…The successful application of the developed method to the determination of taurine in tear fluids makes the device attractive for clinical and biomedical applications. An interesting work recently published proposes an on-line microdialysis (MD)-CE method with LIF detection to measure the in-vivo dynamics of amino acids (taurine, GABA, and 10 proteinogenic amino acids) biomarkers of metabolism in adipose tissue [17].…”

“…Fluorescence detection has also been widely employed for the analysis of NPAAs due to its high sensitivity; however, a derivatization procedure is also needed due to the lack of fluorescence of most amino acids. Many derivatization reagents such as 2,3-naphthalenedicarboxaldehyde (NDA) [9,10,11,12,13,14], 4fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) [15,16,17,18], fluorescein isothiocyanate (FITC) [19], 9-fluorenylmethyl chloroformate (FMOC-Cl) [20], benzoyl chloride, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC), dansyl chloride (DNS-Cl) [21] and o-phthaldialdehyde (OPA) [16] have been employed. An interesting alternative to these detection approaches is mass spectrometry (MS) that presents higher sensitivity and selectivity than other systems [5] and provides structural information being not necessary a derivatization step although sometimes it is also employed.…”

Recent advances in amino acid analysis by capillary electromigration methods: June 2015–May 2017

“…This allowed a microdialysis time resolution of 1 min. The same microdialysis‐CE approach was developed to measure in‐vivo AA dynamics every 22 s . Several AAs (Arg, Lys, Ile, Leu, Met, Phe, Val, GABA, Glu, Ala, Gly and taurine) were quantified in inguinal adipose mice tissue depots.…”

Capillary Electrophoresis: Trends and Recent Advances

“…CE separations were performed in less than 30 s, and the temporal resolution of the online MD-CE assay was within 60 s. In a next study, the MD-CE assay was used to monitor in vivo dynamics, achieving a temporal resolution of 22 s for small bioamines. 19 …”

“…Analytes were sampled using microdialysis, fluorescently labeled in an online reaction, separated using CE and detected using laser-induced fluorescence (LIF) in a sheath flow cuvette. CE separations were performed in less than 30 s, and the temporal resolution of the online MD-CE assay was within 60 s. In a next study, the MD-CE assay was used to monitor in vivo dynamics, achieving a temporal resolution of 22 s for small bioamines …”