Transcriptomic analysis reveals niche gene expression effects of beta-hydroxybutyrate in primary myotubes
Various forms of fasting, including time-restricted feeding, alternate day fasting, and periodic fasting have shown promise in clinical and pre-clinical studies to normalize body weight, improve metabolic health, and protect against disease. Recent studies suggest that {beta}-hydroxybutyrate ({beta}OHB), a characteristic ketone body of the fasted metabolic state, acts as a potential signaling molecule mediating the beneficial effects of the various forms of fasting, potentially by acting as a histone deacetylase inhibitor. In the first part we investigated whether {beta}OHB, in comparison to the well-established histone deacetylase inhibitor butyrate, influences cellular differentiation in vitro. In C2C12 myotubes, 3T3-L1 adipocytes, and THP-1 monocytes, millimolar concentrations of {beta}OHB did not alter differentiation, as determined by gene expression and histological assessment, whereas equimolar concentrations of butyrate potently impaired differentiation in all cell types. RNA-sequencing revealed that unlike butyrate, {beta}OHB minimally impacted gene expression in adipocytes, macrophages, and hepatocytes. However, in myocytes, {beta}OHB upregulated genes involved in the TCA cycle and oxidative phosphorylation, while downregulating genes belonging to cytokine and chemokine signal transduction. Overall, our data do not support the notion that {beta}OHB serves as a powerful signaling molecule regulating gene expression in adipocytes, macrophages and hepatocytes, but suggest that {beta}OHB may act as a niche signaling molecule in muscle.