What are HDL's primary responsibilities in the body?

High-Density Lipoproteins (HDL) play a critical role in lipid metabolism and cardiovascular health. One of the primary responsibilities of HDL is to carry cholesterol from peripheral tissues back to the liver. This process is often referred to as reverse cholesterol transport. By facilitating the removal of cholesterol from cells and transporting it to the liver, HDL helps in recycling and excretion, thereby reducing the risk of atherosclerosis and cardiovascular diseases.

This function is essential in maintaining healthy cholesterol levels and protecting against the accumulation of excess cholesterol in the arterial walls. As a result, higher levels of HDL are often associated with a lower risk of heart disease.

The other options do not accurately reflect the main functions of HDL. For instance, while muscles do utilize fatty acids for energy, HDL does not transport cholesterol directly to them. Similarly, glucose delivery to the brain is primarily managed by the bloodstream and not specifically through HDL. Lastly, maintaining muscle mass during exercise is more related to protein metabolism and the action of various hormones rather than the specific role of HDL.