HDLs and LDLs

Last week, we visited Dr. Daniela Valensin’s lab, where we performed an NMR analysis on olive oil. Nuclear magnetic resonance is used to characterize the olive oil and can help evaluate its nutritional content. For example, NMR can be used to which saturated, monounsaturated, and polyunsaturated fats are present in olive oil. One particular item of interest that I learned on this trip, however, was that olive oil is considered to be a healthy alternative to vegetable oils because of its high levels of monounsaturated fats and minimal levels of trans-unsaturated fats. High levels of monounsaturated fats are good because they help lower LDL (bad) cholesterol levels and raise HDL (good) cholesterol levels.

Cholesterol and fatty acids are packaged into complexes known as lipoproteins with proteins by the liver in varying degrees of density, including chylomicrons (which are the least dense, largest, and contain the least protein) to LDLs (low density lipoproteins) which are slightly more dense than chylomicrons to HDLs (high density lipoproteins) which are the most dense and contain the highest levels of proteins. High levels of HDLs are good because the complexes carry proteins that aid in the absorption of cholesterol from cell membranes and transport back to the liver. Consequently, HDLs help lower blood cholesterol levels.

LDLs, on the other hand, function primarily to carry cholesterol to tissues. Excessive levels of cholesterol in cell membranes can be problematic because it increases the permeability of the membrane, possibly allowing unwanted, and perhaps harmful, materials to enter the cell. In addition, extremely high levels of LDLs in the bloodstream can promote a pathway through which LDLs are absorbed by the cell and oxidized, leading to the inflammatory response known as atherosclerosis. Conversely, HDLs can be potentially anti-inflammatory because they inhibit the oxidation of LDLs that leads to this atherosclerosis.

References: http://en.wikipedia.org/wiki/High_density_lipoprotein