Mouse skeletal muscle and liver in response to physiological insulin

Regulation of gene expression is an important aspect of insulin’s physiological action, however, most studies rely on in vitro systems or pharmacological doses of insulin. Here, we demonstrate that under euglycemic-clamp conditions, physiological levels of insulin regulate over 1500 transcripts in muscle and 1000 transcripts in liver. These include expected pathways related to glucose and lipid utilization, mitochondrial function and autophagy in muscle, and glucose production and steroidogenesis in liver, as well as unexpected pathways, such as mRNA splicing, chromatin remodeling, and regulation of hepatocyte nuclear factors. Insulin also regulates over 100 non-coding RNAs in muscle and liver. These changes in coding and non-coding RNAs, refined by alternative splicing, provide an integrated transcriptional network underlying the complexity of insulin action in vivo. Three month-old male C57BL/6J mice (n = 6 per condition) were anestethized and had an indwelling catheter placed in the right internal jugular vein. After recovery (4-5 days), conscious mice were continuously perfused with either 4 or 12 mU/kg/min insulin or saline as control. Blood glucose was verified every 5-30 min and adjusted with infusion of a 20% glucose solution. At 20 min or 3 h of clamp, mice were euthanized by cervical dislocation, and tissues were harvested, snap frozen in liquid nitrogen and kept at -80 oC. Total RNA was isolated from quadriceps muscle and liver fragments. Stranded cDNA libraries with unique index tags for each sample (48 multiplexed) were made using a directional RNA-seq kit (Wafergen). Sequencing was performed on an Illumina HiSeq 2500 run on rapid mode (2x50).