Biomarkers for Obesity: In Vivo Monitoring of Bioamine Metabolism in Adipose Tissue and Skeletal Muscle Using Online Microdialysis-Capillary Electrophoresis

Abstract

Significant work has been done studying the metabolism of adipose tissue in recent years, in an effort to more effectively combat the obesity epidemic. Adipose tissue has been found to participate in the metabolism signaling network, with BCAAs playing a vital role as messengers relating the amino acid content of high protein meals. BCAA plasma levels have also been found to be elevated in individuals with obesity or type 2 diabetes, with their increased levels often occurring prior to elevated resting glucose levels and insulin resistance. Their dynamics under various metabolic conditions must still be examined however, on a metabolically relevant time scale. Current methods are limited in their time response for in vivo studies, with time-points ranging from minutes to hours. Metabolic dynamics must be studied in near real time, in order to establish these bioamines as metabolic biomarkers. In this work, an in vivo platform is developed for monitoring bioamine metabolism dynamics in adipose tissue and skeletal muscle with 22 second temporal resolution. A high-speed online microdialysis-CE assay, capable of detecting BCAAs and their related metabolites, is utilized to monitor dynamics in near real time. Inguinal adipose tissue and quadriceps skeletal muscle serve as the sampling locations in C57BL6 mice. A systemic stimulation of insulin demonstrated our assay’s ability to detect induced metabolic dynamics. Stimulations of glucose, saccharin, and ace K provide further information regarding the metabolism of bioamines in adipose tissue.