Carb-loading: Freeze-induced activation of the glucose-responsive ChREBP transcriptional network in wood frogs

AbstractThe freeze-tolerant wood frog, Rana sylvatica, is one of few vertebrate organisms that can tolerate freezing, with up to 70% of its total body water being converted into extracellular ice. Physiologically, wood frogs show no signs of muscle movement, breathing, heartbeat, or brain activity for several weeks or months at a time but emerge unharmed upon thawing. Given that wood frogs rely mainly on carbohydrate metabolism during freezing, the involvement of the carbohydrate-responsive element-binding protein (ChREBP) in response to freezing is of interest. In liver tissue, protein and transcript levels of ChREBP increased by 1.4±0.09‐fold and 1.9±0.26‐fold, respectively, and nuclear distribution and DNA-binding activity rose by 2.0±0.08‐fold and 1.5±0.08‐fold, respectively. This enhanced transcriptional activity of ChREBP was corroborated by increased transcript expression of select downstream genes of fatty acid synthase, pyruvate kinase, and stearoyl-CoA desaturase in liver tissue. While liver tis...