Melanocortin signaling in the CNS directly regulates circulating cholesterol

Abstract

This study finds that inhibition of the hypothalamic melanocortin receptors increases the level of high-density lipoprotein HDL-C, a form of cholesterol, circulating in the blood stream. Uptake of HDL-C into the liver was slowed, as expression of one of the hepatic cholesterol receptors was downregulated. Cholesterol circulates in the blood in association with triglycerides and other lipids, and elevated blood low-density lipoprotein cholesterol carries a risk for metabolic and cardiovascular disorders, whereas high-density lipoprotein (HDL) cholesterol in the blood is thought to be beneficial. Circulating cholesterol is the balance among dietary cholesterol absorption, hepatic synthesis and secretion, and the metabolism of lipoproteins by various tissues. We found that the CNS is also an important regulator of cholesterol in rodents. Inhibiting the brain's melanocortin system by pharmacological, genetic or endocrine mechanisms increased circulating HDL cholesterol by reducing its uptake by the liver independent of food intake or body weight. Our data suggest that a neural circuit in the brain is directly involved in the control of cholesterol metabolism by the liver.