Role of Apolipoproteins in Neurodegenerative Diseases

Since lipids are insoluble in water, they are carried in the blood as particles called lipoproteins. Lipoproteins consisting of lipids and proteins are multicomponent complexes. The classification of lipoproteins, which are divided into several main groups such as low density lipoprotein (LDL), high density lipoprotein (HDL), very low density lipoprotein (VLDL) and chylomicrons, is based on their density, size, lipid and apolipoprotein content. Apolipoproteins are the protein component of lipoproteins that carry lipids from the blood to various tissues of the body for metabolism and utilisation. Apolipoproteins play an important role in lipid metabolism. They regulate many metabolic enzymes and interact with lipoprotein receptors. Numerous studies have shown that apolipoprotein phenotype, different allelic polymorphism and apolipoprotein gene mutation can affect metabolism and utilisation of blood lipids and consequently trigger the onset and development of atherosclerosis, hyperlipidaemia, cerebrovascular and cardiovascular diseases. Furthermore, apolipoproteins have been associated with neurodegenerative diseases and different apolipoprotein polymorphisms have been evaluated as risk factors or protective agents in different neurodegenerative diseases. This review presents evidence from some studies linking apolipoproteins with Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration disease.