Hepatic fructose metabolism is antagonized by growth hormone/insulin-like growth factor signaling via regulation of ketohexokinase expression
Overconsumption of added sugars such as fructose has been associated with a remarkable decline in metabolic health. Fructose is primarily metabolized by the small intestines and the liver, via phosphorylation mediated by ketohexokinase (KHK). KHK activity is traditionally viewed as lacking negative feedback mechanisms, such as those present to limit glucose metabolism, leading to excessive fat accumulation characteristic of metabolic dysfunction-associated liver disease (MASLD). In this study, we observe KHK downregulation in hepatocytes of diet-induced and genetic models of MASLD. Reduced KHK coincides with decreased flux of fructose-derived carbons into glycolytic and amino acid metabolic pathways, suggesting the presence of mechanisms that limit KHK-mediated fructolysis in the liver. We subsequently focused on the growth hormone (GH)/insulin-like growth factor (IGF) signaling pathway as a potential mechanism antagonizing KHK expression. In transgenic mice with enhanced GH signaling, KHK levels are reduced, whereas reduced GH activity leads to increased KHK expression. Additionally, administration of GH and IGF-1 in liver cell cultures induces time-dependent degradation of KHK, facilitated by direct interactions between KHK and the IGF-1 receptor (IGF-1R). Single-nuclei RNA sequencing revealed elevated IGF-1R expression in hepatocytes from diet-induced MASLD mice, supported by human MASLD patient samples, which also show reduced KHK expression. Taken together, these findings describe a novel pathway by which GH/IGF-1 signaling regulates KHK, offering new insights into how the liver adapts to metabolic stress to limit fructose-driven liver dysfunction.