Changes in gene expression play a role in adapting hepatic metabolism on longer time scales to for example reduce futile cycles in counteracting pathways (like down-regulation of glucokinase and up-regulation of glucose-6 phosphatase under hypoglycemia) or match glucose metabolism to physiological requirements (up-regulating of glucose-6 phosphatase under hypoglycemic conditions to increase gluconeogenesis). The gene discussed is GCK; the disease is Hypoglycemia.