Leptin (produced in adipose cells) - Feedback mechanism signals to inhibit food intake and to regulate body weight - In response to adequate fat stores, leptin inhibits insulin secretion - In obese humans, leptin levels are increased, exacerbating hyperglycaemia - Leptin resistance is thought to exist in the obese state, with lack of inhibition of food intake - Insulin and glucagon secretion are also under neuronal control - Vagal (cholinergic) stimulation leads to the release of insulin - α-sympathetic stimulation strongly inhibits insulin release - β-sympathetic fibres stimulate it