Obesity and free fatty acids: double trouble

The socio-economic impact of obesity, one of the most prevalent medical disorders in Western society, is mainly due to its association with a higher risk of coronary heart disease. It is likely that atherosclerosis develops against a background of obesity as a result of the insulin resistance that is invariably present in overweight and obese subjects. Fasting plasma lipids may be normal in obese subjects, but they are usually affected by postprandial hyperlipidemia, which is probably due to competition between chylomicrons and VLDL for the same metabolic pathways. The basis for the impaired clearance of atherogenic chylomicron remnants is the fact that obesity causes hepatic apo B-VLDL overproduction, and thus leads to competition with chylomicrons and their remnants at the lipolytic pathway (lipoprotein lipase and hepatic lipase) and receptor level (LDL-receptor and remnant-receptor). The overproduction of VLDL is probably caused by an enhanced hepatic flux of free fatty acids in both the postprandial (from the lipolysis of triglyceride rich particles) and postabsorptive states (from adipocytes). Weight reduction by means of life-style changes, supported by medical interventions with inhibitors of intestinal fat absorption (e.g. Orlistat) or appetite suppressants (e.g. Sibutramine), is essential in order to decrease the risk of atherosclerosis. Furthermore, improvement of risk factors can be achieved by means of fibrate treatment to modulate fasting and postprandial triglyceride levels. Treatment with cholesterol synthesis inhibitors ("statins") may reduce hepatic VLDL production and increase the clearance of atherogenic remnants by upregulating LDL-receptors, thus leading to improved fasting lipid levels and enhanced clearance of chylomicron remnants. Finally, the use of thiazolidinedione derivatives to improve insulin sensitivity may be one of the options for reducing the risk of atherosclerosis in obese subjects.