How is metabolism coordinated between tissues in fed and fasting states?

Metabolic integration ensures appropriate nutrient distribution based on energy state. In the fed state: insulin signals abundance, promoting glucose uptake in muscle/adipose, glycogen synthesis in liver/muscle, lipogenesis in liver/adipose, and protein synthesis. Liver takes up glucose and synthesizes fatty acids for export. In fasting: glucagon and cortisol signal depletion, liver performs gluconeogenesis and ketogenesis, adipose releases fatty acids, muscle oxidizes fatty acids and ketone bodies while releasing amino acids for gluconeogenesis. Brain shifts from glucose to ketone bodies during prolonged fasting. This inter-organ cooperation maintains blood glucose, supplies appropriate fuels to each tissue, and preserves muscle protein. Hormones, metabolite concentrations, and neural signals coordinate these responses.