5th February 2024

Lipid metabolism

Introduction

Lipids are large, water-insoluble molecules that store energy and serve as cellular membranes and lipoprotein components.

Most lipids in the human body from ingesting food are triglycerides and cholesterols. 

Other lipids in the body may include fatty acids and membrane lipids (phospholipids, sphingolipids, glycolipids and glycerophospholipids). 

Physiology

Lipid digestion and absorption are the main steps in lipid metabolism. Once digested and absorbed by the gastrointestinal systems, fatty acids and monoglycerides are recombined back into triglycerides. Triglycerides and cholesterol are packaged into chylomicrons, which travel through the bloodstream to enter adipose and other body tissues. As membrane lipids, triglycerides, and cholesterols are hydrophobic, a transport protein known as lipoprotein allows these lipid molecules to be transported through blood. Lipids are stored in white adipose tissue as triglycerides, formed from a backbone of glycerol + 3 fatty acids.

Once chylomicrons and other lipoproteins travel through tissues, lipoprotein lipase will break down these particles to release triglycerides into fatty acids and glycerol. The main steps of fatty acid catabolism occur in the mitochondria. Long-chain fatty acids must be converted to fatty-acyl-CoA to pass the mitochondrial membrane.

References

Natesan V, Kim SJ. Lipid Metabolism, Disorders and Therapeutic Drugs–Review. Biomolecules & therapeutics. 2021 Nov 11;29(6):596.