*Geek Box: Very-Low-Density Lipoprotein
Most people are very familiar with low-density lipoprotein – LDL, the “bad cholesterol” – but not as familiar with its very-low cousin, VLDL. But we should be, because VLDL is hugely important in the overall picture of both metabolic health, particularly as it relates to liver fat, and cardiovascular health, as it relates to circulating cholesterol and cholesterol transport. We have two main pathways of fat metabolism, one is exogenous and the other endogenous.
The exogenous pathway takes in the fat – triglycerides – we consume through diet, which are transported from intestinal cells by chylomicrons. The endogenous pathway takes triglycerides that are synthesised in the liver from circulating free fatty acids, a majority of which are broken down from storage, i.e., adipose tissue lipolysis. These triglycerides also need a vehicle to carry them out of the liver to tissues which can use or store them, and this vehicle is VLDL, which is secreted by the liver.
There are broadly two types, which are differentiated by their content of triglycerides. VLDL1 is very large and rich in triglycerides; VLDL2 is depleted of triglycerides and is a smaller and more dense VLDL particle. Thus, the primary relevance of the ‘1’ after VLDL is that it denotes the larger VLDL particles, which carry more triglycerides.