Next Generation Sequencing Facilitates Quantitative Analysis of Wild Type and 2.5ppm iAs Treated Mouse Gastrocnemius Muscle Transcriptomes

Inorganic arsenic (iAs) is a widespread environmental toxin. In addition to being a human carcinogen, its effect on systemic glucose metabolism has started to gain recognition recently. However, its in vivo effect on insulin sensitivity is not clear. Here we use mouse models to dissect the dose-dependent effects of iAs in glucose metabolism. We found that a low-dose exposure (0.25 ppm iAs in drinking water) caused glucose intolerance in adult male C57BL/6 mice, likely by disrupting glucose-induced insulin secretion without affecting peripheral insulin sensitivity. However, a higher-dose exposure (2.5 ppm iAs) has diminished effects on glucose tolerance despite disrupted pancreatic insulin secretion. We performed hyperinsulinemic euglycemic clamp, the gold standard analysis of systemic insulin sensitivity, and found that the 2.5 ppm iAs enhanced systemic insulin sensitivity by simultaneously enhancing insulin-stimulated glucose uptake in skeletal muscles and insulin-mediated suppression of endogenous glucose production. RNA-seq analysis of muscles revealed that 2.5 ppm iAs regulated expression of many genes involved in the metabolism of fatty acids, pyruvate, and amino acids. These findings suggest that iAs has distinct effects on distinct metabolic tissues at different dose thresholds, which could help reconcile some of the conflicting epidemiological results. The study shed light on the complex interactions between an environmental factor and the systemic glucose metabolism. Gastrocnemius Muscle mRNA profiles of 24-week 2.5 ppm iAs in drinking water treatment and control mice were generated by deep sequencing, in triplicate, using Illumina HiSeq 3000.